Immune response inducer

ABSTRACT

An immunity-inducing agent comprising as an effective ingredient a specific polypeptide is disclosed. These polypeptides were isolated, by the SEREX method using a cDNA library derived from canine testis and serum from a cancer-bearing dog, as a polypeptide which binds to an antibody existing specifically in serum derived from a cancer-bearing living body. The polypeptides can induce immunity in a living body and cause regression of a tumor in a cancer-bearing living body. Therefore, these polypeptides are especially effective as a therapeutic and/or prophylactic agent for a cancer(s).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No. 12/739,723 filed on Apr. 23, 2010, which is the National Stage of PCT International Application No. PCT/JP2008/069267, filed on Oct. 23, 2008, which claims priority to Patent Application Nos. 2007-277578, 2007-277611, 2007-277240 and 2007-279113, filed in Japan on Oct. 25, 2007, Oct. 25, 2007, Oct. 25, 2007 and Oct. 26, 2007, all of which are hereby expressly incorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a novel immunity-inducing agent useful as a therapeutic and/or prophylactic agent for a cancer(s).

BACKGROUND ART

Cancers are the commonest cause for death among all of the causes for death, and the therapies therefor are mainly surgical treatment in combination with radiotherapy and chemotherapy. In spite of the developments of new surgical methods and discovery of new anti-cancer agents in recent years, treatment results of cancers are not improved very much at present except for some cancers. In recent years, by virtue of the development in molecular biology and cancer immunology, cancer antigens recognized by cytotoxic T cells reactive with cancers, as well as the genes encoding the cancer antigens, were identified, and expectations for antigen-specific immunotherapies have been raised (see Non-patent Literature 1). In immunotherapy, to reduce side effects, it is necessary that the peptide or protein recognized as the antigen exist hardly in normal cells and exist specifically in cancer cells. In 1991, Boon et al. of Ludwig Institute in Belgium isolated human melanoma antigen MAGE 1 recognized by CD8-positive T cells by a cDNA-expression cloning method using an autologous cancer cell line and cancer-reactive T cells (see Non-patent Literature 2). Thereafter, the SEREX (serological identifications of antigens by recombinant expression cloning) method, wherein tumor antigens recognized by antibodies produced in the living body of a cancer patient in response to the cancer of the patient himself are identified by application of a gene expression cloning method, was reported (Non-patent Literature 3; Patent Literature 1), and various cancer antigens have been isolated (see Non-patent Literatures 4 to 9). Using a part thereof as targets, clinical tests for cancer immunotherapy have started.

On the other hand, as in human, a number of tumors such as mammary gland tumor and squamous cell carcinoma are known in dogs and cats, and they rank high also in the statistics of diseases in dogs and cats. However, at present, no therapeutic, prophylactic or diagnostic agents exist which are effective for cancers in dogs and cats. Most of tumors in dogs and cats are realized by owners only after they advance to grow bigger, and in many cases, it is already too late to visit a hospital to receive surgical excision of the tumor or administration of a human drug (an anticancer preparation or the like), so that those dogs and cats die shortly after the treatment. Under such circumstances, if therapeutic agents, prophylactic agents and diagnostic agents for cancers effective for dogs and cats become available, their uses for canine cancers are expected to be developed.

-   Patent Literature 1: U.S. Pat. No. 5,698,396 B -   Non-patent Literature 1: Tsuyoshi Akiyoshi, Cancer and Chemotherapy,     24, 551-519 (1997) -   Non-patent Literature 2: Bruggen P. et al., Science, 254:1643-1647     (1991) -   Non-patent Literature 3: Proc. Natl. Acad. Sci. USA, 92:11810-11813     (1995) -   Non-patent Literature 4: Int. J. Cancer, 72:965-971 (1997) -   Non-patent Literature 5: Cancer Res., 58:1034-1041 (1998) -   Non-patent Literature 6: Int. J. Cancer, 29:652-658 (1998) -   Non-patent Literature 7: Int. J. Oncol., 14:703-708 (1999) -   Non-patent Literature 8: Cancer Res., 56:4766-4772 (1996) -   Non-patent Literature 9: Hum. Mol. Genet 6:33-39, 1997 -   Non-patent Literature 10: Naokazu Inoue, Ryo Yamaguchi and Masahito     Ikawa, Protein, Nucleic Acid and Enzyme, Vol. 50, No. 11, 1405-1412 -   Non-patent Literature 11: J Cell Sci. 115:1825-35 -   Non-patent Literature 12: Blood. 95:1788-96 -   Non-patent Literature 13: Mol Endocrinol. 9:243-54 (1995) -   Non-patent Literature 14: J Cell Biol. 145: 83-98 (1999)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a novel immunity-inducing agent which is useful as a therapeutic and/or prophylactic agent for a cancer(s)

Means for Solving the Problems

The present inventors intensively studied to obtain a cDNA encoding a protein which binds to an antibody existing in serum derived from a cancer-bearing living body by the SEREX method using a cDNA library derived from canine testis and serum of a cancer-bearing dog, which cDNA was used to prepare a polypeptide having the amino acid sequence shown in SEQ ID NO:2, a canine calmegin protein having the amino acid sequence shown in SEQ ID NO:16, a canine centrosomal protein (which may be hereinafter abbreviated as CEP) having the amino acid sequence shown in SEQ ID NO:26, and the canine thyroid hormone receptor interactor 11 (which may be hereinafter described as “TRIP11”) having the amino acid sequence shown in SEQ ID NO:39. Further, based on a registered canine gene having a high homology to the canine CEP of the above-described SEQ ID NO:26, a canine CEP having the amino acid sequence shown in SEQ ID NO:28 was prepared. Further, based on a human gene homologous to the obtained gene, a polypeptide having the amino acid sequence shown in SEQ ID NO:4, a human calmegin protein having the amino acid sequence shown in SEQ ID NO:18, a human CEP having the amino acid sequence shown in SEQ ID NO:30, and a human TRIP11 having the amino acid sequence shown in SEQ ID NO:41 were prepared. The inventors then discovered that these polypeptides can induce immunocytes in a living body and cause regression of an already occurred tumor when administered to the living body, thereby completing the present invention.

That is, the present invention provides an immunity-inducing agent comprising as an effective ingredient any one of the polypeptides (a) to (c) below, the polypeptide having an immunity-inducing activity, or as an effective ingredient a recombinant vector which comprises a polynucleotide encoding the polypeptide and is capable of expressing the polypeptide in vivo: (a) a polypeptide consisting of not less than 7 consecutive amino acids of the amino acid sequence shown in SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 in SEQUENCE LISTING; (b) a polypeptide having a homology of not less than 80% to the polypeptide (a) and consisting of not less than 7 amino acids; and (c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence thereof. The present invention also provides a method for inducing immunity, the method comprising administering to an individual an effective amount of any one of the above-described polypeptides (a) to (c), the polypeptide having an immunity-inducing activity, or an effective amount of a recombinant vector which comprises a polynucleotide encoding the polypeptide and is capable of expressing the polypeptide in vivo. The present invention further provides a method for treating antigen-presenting cells, the method comprising bringing any one of the above-described polypeptides (a) to (c), the polypeptide having an immunity-inducing activity, into contact with antigen-presenting cells. The present invention further provides use of any one of the above-described polypeptides (a) to (c), the polypeptide having an immunity-inducing activity, or a recombinant vector which comprises a polynucleotide encoding the polypeptide and is capable of expressing the polypeptide in vivo, for production of an immunity-inducing agent.

Effect of the Invention

By the present invention, a novel immunity-inducing agent useful as a therapeutic and/or prophylactic agent for a cancer(s) was provided. As indicated in the Examples below, the polypeptide used in the present invention can induce immunocytes in a cancer-bearing dog and also can cause reduction or regression of an already occurred tumor when administered to a cancer-bearing dog. Therefore, the polypeptide is useful for therapy and prophylaxis of a cancer(s).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the expression pattern of the gene identified in Example A-1 in normal tissues and tumor cell lines. Reference numeral 1: the expression pattern of the identified gene; Reference numeral 2: the expression pattern of the GAPDH gene.

FIG. 2 shows the detection by Coomassie staining of the canine-derived protein produced in E. coli and purified in Example A, which protein was identified in the present invention. Reference numeral 3: the band for the canine-derived protein of the present invention.

FIG. 3 shows the expression pattern of the calmegin gene identified in the present invention in normal tissues and tumor cell lines. Reference numeral 1: the expression pattern of the calmegin gene; Reference numeral 2: the expression pattern of the GAPDH gene.

FIG. 4 shows the detection by Coomassie staining of the canine calmegin protein, which is an example of the polypeptide used in the present invention, produced in E. coli and purified in Example B. Reference numeral 3: the band for the canine calmegin protein.

FIG. 5 shows the expression pattern of the gene encoding the CEP protein in normal tissues and tumor cell lines. Reference numeral 1: the expression pattern of the gene encoding the CEP protein; Reference numeral 2: the expression pattern of the GAPDH gene.

FIG. 6 shows the detection by Coomassie staining of the canine CEP of SEQ ID NO:26, which is an example of the polypeptide used in the present invention, produced in E. coli and purified in Example C. Reference numeral 3: the band for the canine CEP protein.

FIG. 7 shows the expression pattern of the gene encoding the TRIP11 protein in normal tissues and tumor cell lines. Reference numeral 1: the expression pattern of the gene encoding the TRIP11 protein; Reference numeral 2: the expression pattern of the GAPDH gene.

FIG. 8 shows the detection by Coomassie staining of the canine TRIP11 protein, which is one of the polypeptides used in the present invention, produced in E. coli and purified in Example D. Reference numeral 3: the band for the canine TRIP11 protein.

BEST MODE FOR CARRYING OUT THE INVENTION

The polypeptides contained in the immunity-inducing agents of the present invention as effective ingredients are as follows. It should be noted that the term “polypeptide” in the present invention means a molecule formed by peptide bonding of a plurality of amino acids, and includes not only polypeptide molecules having large numbers of amino acids constituting them, but also low molecular weight molecules having small numbers of amino acids (oligopeptides) and full-length proteins. Thus, in the the present invention, proteins consisting of the full length of SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 are also included in “polypeptide”.

(a) A polypeptide which consists of not less than 7 consecutive amino acids of a polypeptide having the amino acid sequence shown in SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 in SEQUENCE LISTING and has an immunity-inducing activity.

(b) A polypeptide which has a homology of not less than 80% to the polypeptide (a), consists of not less than 7 amino acids, and has an immunity-inducing activity.

(c) A polypeptide which comprises the polypeptide (a) or (b) as a partial sequence thereof and has an immunity-inducing activity.

It should be noted that the term “having the amino acid sequence” in the present invention means that amino acid residues are aligned in that order. Accordingly, for example, “a polypeptide having the amino acid sequence shown in SEQ ID NO:2” means a polypeptide having a size of 306 amino acid residues, whose amino acid sequence is Met Ala Ala Leu . . . (snip) . . . Ile Thr Ser Pro as shown in SEQ ID NO:2. Further, “a polypeptide having the amino acid sequence shown in SEQ ID NO:2” may be abbreviated as “a polypeptide of SEQ ID NO:2”. This also applies to the term “having the base sequence”.

As used herein, the term “immunity-inducing activity” means an ability to induce immunocytes which secrete cytokines such as interferon in a living body. Whether or not a polypeptide has an immunity-inducing activity can be confirmed using, for example, the known ELISPOT assay. More particularly, for example, as described in the Examples below, cells such as peripheral blood mononuclear cells are obtained from a living body to which a polypeptide whose immunity-inducing activity is to be evaluated was administered, which cells are then cocultivated with the polypeptide, followed by measuring the amount of a cytokine produced by the cells using a specific antibody, thereby measuring the number of immunocytes in the cells, which enables evaluation of the immunity-inducing activity. Further, as described in the Examples below, a recombinant polypeptide prepared based on the amino acid sequence of SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 can cause regression of a tumor by its immunity-inducing activity when administered to a cancer-bearing living body. Therefore, the above-described immunity-inducing activity can be evaluated also as the ability to inhibit the growth of cancer cells expressing the polypeptide of SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 or to cause reduction or disappearance of a cancer tissue (tumor) (hereinafter referred to as “anti-tumor activity”). The anti-tumor activity of a polypeptide can be confirmed by, for example, observation of whether or not the tumor is reduced when the polypeptide was administered to a cancer-bearing living body, as more particularly described in the Examples below. Further, the anti-tumor activity of a polypeptide can be evaluated also by observation of whether or not T cells stimulated with the polypeptide (that is, T cells brought into contact with antigen-presenting cells which present the polypeptide) show a cytotoxic activity against tumor cells in vitro. The contact between T cells and antigen-presenting cells can be carried out by cocultivation of the both in a liquid medium, as mentioned below. Measurement of the cytotoxic activity can be carried out by, for example, a known method called 51Cr release assay described in Int. J. Cancer, 58:p317, 1994. In cases where a polypeptide is used for therapy and/or prophylaxis of a cancer(s), the evaluation of the immunity-inducing activity is preferably carried out using the anti-tumor activity as an index, although the index is not restricted.

The amino acid sequence shown in SEQ ID NO:2 in SEQUENCE LISTING is the amino acid sequence of the polypeptide with unknown function isolated as a polypeptide which binds to an antibody existing specifically in serum derived from a cancer-bearing dog, which isolation was carried out by the SEREX method using a canine testis-derived cDNA library and serum of a cancer-bearing dog (see Example A-1). It is registered in the NCBI database under Accession No. XP_535343 (protein) and Accession No. XM_535343 (coding gene), but its function has not been reported. Further, the amino acid sequence shown in SEQ ID NO:4 is an amino acid sequence of a human homologous factor of the polypeptide of SEQ ID NO:2 isolated as described above. This human homologous factor is also a protein whose function is unknown, which is registered in the NCBI database under Accession No. NP_689873 (protein) and Accession No. NM_152660 (coding gene). The homology between them is 93% in terms of base sequence and 99% in terms of amino acid sequence.

The respective amino acid sequences shown in SEQ ID NOs:16 and 18 are those of the calmegin protein isolated as a polypeptide and a human homologous factor thereof, which polypeptide binds to an antibody existing specifically in serum derived from a cancer-bearing dog, which isolation was carried out by the SEREX method using a canine testis-derived cDNA library and serum of a cancer-bearing dog (see Example B-1). Calmegin was identified as a protein which is expressed specifically at the time of differentiation of a spermatid, and it has a chaperone activity in vitro. Since it is expressed only in testis and disappears in a mature sperm, calmegin is considered to have a function to fold proteins involved in differentiation of spermatid (Non-patent Literature 10, Naokazu Inoue, Ryo Yamaguchi and Masahito Ikawa, Protein, Nucleic Acid and Enzyme, Vol. 50, No. 11, 1405-1412). However, there has been no report showing that the protein is expressed in a cancer and useful for therapy or prophylaxis thereof. The homology between the canine calmegin gene and the human calmegin gene is 90% in terms of base sequence and 89% in terms of amino acid sequence.

The respective amino acid sequences shown in SEQ ID NOs:26, 28 and 30 are those of the CEP isolated as a polypeptide, a canine factor having a high homology to the polypeptide and a human homologous factor of the polypeptide, which polypeptide binds to an antibody existing specifically in serum derived from a cancer-bearing dog, which isolation was carried out by the SEREX method using a canine testis-derived cDNA library and serum of a cancer-bearing dog (see Example C-1). CEP is a protein which is required by the centrosome to control microtubules and also involved in maturation of the centrosome. It is known that chromosomal translocation frequently occurs in some of myeloproliferative disorders, and since the CEP gene exists at the point where the translocation occurs, CEP is considered to have a certain relationship with the disorders. However, there has been no report showing that the protein is expressed in a cancer and useful for therapy or prophylaxis thereof (Non-patent Literature 11: J Cell Sci. 115:1825-35; Non-patent Literature 12: Blood. 95:1788-96). The homology between the canine CEP gene encoding the CEP of SEQ ID NO:26 and the human CEP gene is 87% in terms of base sequence and 84% in terms of amino acid sequence.

The respective amino acid sequences shown in SEQ ID NOs:39 and 41 are those of the TRIP11 protein isolated as a polypeptide and a human homologous factor thereof, which polypeptide binds to an antibody existing specifically in serum derived from a cancer-bearing dog, which isolation was carried out by the SEREX method using a canine testis-derived cDNA library and serum of a cancer-bearing dog (see Example D-1). TRIP11 (thyroid hormone receptor interactor 11) was first identified as a factor which interacts with the thyroid hormone receptor β, and its binding to Golgi bodies and microtubules also became evident, so that TRIP11 is considered to play a role in maintaining the shapes of these organelles. However, there has been no report showing that the protein is expressed in a cancer and useful for therapy or prophylaxis thereof (Non-patent Literature 13, Mol Endocrinol. 9:243-54 (1995); Non-patent Literature 14, J Cell Biol. 145: 83-98 (1999)). The homology between the canine TRIP11 gene and the human TRIP11 gene is 88% in terms of base sequence and 86% in terms of amino acid sequence.

The polypeptide (a) consists of not less than 7 consecutive, preferably not less than 9 consecutive amino acids of a polypeptide having the amino acid sequence shown in SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41, and has an immunity-inducing activity. The polypeptide especially preferably has the amino acid sequence shown in SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41. As known in the art, a polypeptide consists of not less than about 7 amino acid residues can exert its antigenicity. Thus, a polypeptide consists of not less than 7 consecutive amino acid residues of the amino acid sequence shown in SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 can have an immunity-inducing activity, so that it can be used for preparation of the immunity-inducing agent of the present invention. However, in view of the fact that antibodies produced against antigenic substances in a living body are polyclonal antibodies, it is thought that an antigenic substance composed of larger number of amino acid residues can induce more types of antibodies which can recognize various sites on the antigenic substance, thereby attaining higher immunity-inducing activity. Therefore, in order to increase the immunity-inducing activity, in the case of SEQ ID NO:2 or 4, the number of the amino acid residues may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 200, still more preferably not less than 250. In the case of SEQ ID NO:16 or 18, the number of the amino acid residues may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 200, still more preferably not less than 400, still more preferably not less than 550. In the case of SEQ ID NO:26, 28 or 30, the number of the amino acid residues may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 300, still more preferably not less than 600, still more preferably not less than 1000, still more preferably not less than 1500, still more preferably not less than 2000. In the case of SEQ ID NO:39 or 41, the number of the amino acid residues may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 300, still more preferably not less than 600, still more preferably not less than 1000, still more preferably not less than 1500.

As a principle of immune induction by administration of a cancer antigenic polypeptide, the following process is known: the polypeptide is incorporated into an antigen-presenting cell and then degraded into smaller fragments by peptidases in the cell, followed by presentation of the fragments on the surface of the cell. The fragments are then recognized by a cytotoxic T cell or the like, which selectively kills cells presenting the antigen.

The size of the polypeptide presented on the surface of the antigen-presenting cell is relatively small and about 7 to 30 amino acids. Therefore, from the view point of presenting thereof on the surface of the antigen-presenting cell, a polypeptide consisting of about 7 to 30, preferably about 9 to 30 consecutive amino acids of the amino acid sequence shown in SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 is sufficient as the above-described polypeptide (a). In some cases, these relatively small polypeptides are presented directly on the surface of the antigen-presenting cells without incorporation thereof into the antigen-presenting cells.

However, as described above, since a polypeptide incorporated into an antigen-presenting cell is cleaved at random sites by peptidases in the cell to yield various polypeptide fragments, which are then presented on the surface of the antigen-presenting cell, administration of a large polypeptide such as the entire region of SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 inevitably causes production of polypeptide fragments by degradation thereof in the antigen-presenting cell, which fragments are effective for immune induction via the antigen-presenting cell. Therefore, for immune induction via antigen-presenting cells, a large polypeptide can also be preferably used. In the case of SEQ ID NO:2 or 4, the number of the amino acids may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 200, still more preferably not less than 250. In the case of SEQ ID NO:16 or 18, the number of the amino acids may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 200, still more preferably not less than 400, still more preferably not less than 550. In the case of SEQ ID NO:26, 28 or 30, the number of the amino acids may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 300, still more preferably not less than 600, still more preferably not less than 1000, still more preferably not less than 1500, still more preferably not less than 2000. In the case of SEQ ID NO:39 or 41, the number of the amino acids may be preferably not less than 30, more preferably not less than 100, still more preferably not less than 300, still more preferably not less than 600, still more preferably not less than 1000, still more preferably not less than 1500.

The above-described polypeptide (b) is the same polypeptide as the above-described polypeptide (a) except that a small number of amino acid residues are substituted, deleted and/or inserted, which has a homology of not less than 80%, preferably not less than 90%, more preferably not less than 95%, still more preferably not less than 98% to the original sequence, and has an immunity-inducing activity. It is well known in the art that, in general, there are cases where a protein antigen retains substantially the same antigenicity as the original even if the amino acid sequence of the protein is modified such that a small number of amino acids are substituted, deleted and/or inserted. Therefore, since the above-described polypeptide (b) may also exert an immunity-inducing activity, it can be used for preparation of the immunity-inducing agent of the present invention. Further, the above-described polypeptide (b) is also preferably the same polypeptide as one having the amino acid sequence shown in SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41 except that one or several amino acid residues are substituted, deleted and/or inserted.

As used herein, the term “homology” of amino acid sequences means a value expressed in percentage which is calculated by aligning two amino acid sequences to be compared such that the number of matched amino acid residues is the maximum, and dividing the number of the matched amino acid residues by the number of the total amino acid residues. When the above-described alignment is carried out, a gap(s) is/are inserted into one or both of the two sequences to be compared as required. Such alignment of sequences can be carried out using a well-known program such as BLAST, FASTA or CLUSTAL W. When a gap(s) is/are inserted, the above-described number of the total amino acid residues is calculated by counting one gap as one amino acid residue. When the thus counted numbers of the total amino acid residues are different between the two sequences to be compared, the homology (%) is calculated by dividing the number of matched amino acid residues by the number of the total amino acid residues in the longer sequence.

The 20 types of amino acids constituting the naturally occurring proteins may be classified into groups each of which has similar properties, for example, into neutral amino acids with side chains having low polarity (Gly, Ile, Val, Leu, Ala, Met, Pro), neutral amino acids having hydrophilic side chains (Asn, Gln, Thr, Ser, Tyr, Cys), acidic amino acids (Asp, Glu), basic amino acids (Arg, Lys, His) and aromatic amino acids (Phe, Tyr, Trp). It is known that, in most cases, substitutions of amino acids within the same group do not change the properties of the polypeptide. Therefore, in cases where amino acid residue(s) in the above described polypeptide (a) in the present invention is/are substituted, the probability that the immunity-inducing activity can be maintained may be made high by conducting the substitution(s) within the same group.

The above-described polypeptide (c) comprises the above-described polypeptide (a) or (b) as a partial sequence and has an immunity-inducing activity. That is, the polypeptide (c) has another/other amino acid(s) or polypeptide(s) added at one or both ends of the polypeptide (a) or (b), and has an immunity-inducing activity. Such a polypeptide can also be used for preparation of the immunity-inducing agent of the present invention.

For example, the above-described polypeptides can be synthesized by a chemical synthesis method such as the Fmoc method (fluorenylmethylcarbonyl method) or the tBoc method (t-butyloxycarbonyl method). Further, they can be synthesized by conventional methods using various commercially available peptide synthesizers. Further, the polypeptide of interest can be obtained by a known genetic engineering method wherein a polynucleotide encoding the above-described polypeptide is prepared and incorporated into an expression vector, which is then introduced into a host cell, in which the polypeptide is produced.

The polynucleotide encoding the above-described polypeptide can be easily prepared by a known genetic engineering method or a conventional method using a commercially available nucleic acid synthesizer. For example, DNA having the base sequence of SEQ ID NO:1, 15, 25, 27 or 38 can be prepared by carrying out PCR using the chromosomal DNA or a cDNA library of a dog as a template and using a pair of primers designed such that the primers can amplify the base sequence described in SEQ ID NO:1, 15, 25, 27 or 38, respectively. DNA having the base sequence of SEQ ID NO:3, 17, 29 or 40 can be prepared similarly by using as the above-described template the human chromosomal DNA or a cDNA library. Conditions for the PCR reaction can be selected as appropriate, and examples of the conditions include, but are not limited to, those wherein a cycle comprising the reaction steps of 94° C. for 30 seconds (denaturing), 55° C. for 30 seconds to 1 minute (annealing), and 72° C. for 2 minutes (extension) is repeated, for example, 30 times, followed by allowing the reaction to proceed at 72° C. for 7 minutes. Further, a desired DNA can be isolated by preparing an appropriate probe or primer based on the information of the base sequence and the amino acid sequence shown in SEQ ID NOs:1 to 4, 15 to 18, 25 to 30, 38 to 41 in SEQUENCE LISTING of the present specification and then using the probe or primer for screening of a cDNA library from a dog or a human. The cDNA library is preferably prepared from cells, an organ or a tissue expressing the protein of SEQ ID NO:2, 4, 16, 18, 26, 28, 30, 39 or 41. Operations such as the above-described preparation of a probe or a primer, construction of a cDNA library, screening of a cDNA library and cloning of a gene of interest are known to those skilled in the art, and can be carried out according to, for example, Molecular Cloning, 2nd Ed. or Current Protocols in Molecular Biology. From the thus obtained DNA, DNA encoding the above-described polypeptide (a) can be obtained. Further, since codons encoding each amino acid are known, the base sequence of a polynucleotide encoding a specific amino acid sequence can be easily specified. Therefore, the base sequences of polynucleotides encoding the above-described polypeptide (b) and polypeptide (c) can also be easily specified, so that such polynucleotides can also be easily synthesized using a commercially available nucleic acid synthesizer according to a conventional method.

The above-described host cells are not restricted as long as they can express the above-described polypeptide, and examples thereof include, but are not limited to, prokaryotic cells such as E. coli; and eukaryotic cells such as mammalian cultured cells including monkey kidney cells COS 1 and Chinese hamster ovary cells CHO, budding yeast, fission yeast, silkworm cells, and Xenopus laevis egg cells.

In cases where prokaryotic cells are used as the host cells, an expression vector having the origin that enables its replication in a prokaryotic cell, a promoter, a ribosome binding site, a DNA cloning site, a terminator and the like is used as the expression vector. Examples of the expression vector for E. coli include the pUC system, pBluescript II, pET expression system and pGEX expression system. By incorporating DNA encoding the above-described polypeptide into such an expression vector and transforming prokaryotic host cells with the vector, followed by culturing the obtained transformant, the polypeptide encoded by the above-described DNA can be expressed in the prokaryotic host cells. In this case, the polypeptide can also be expressed as a fusion protein with another protein.

In cases where eukaryotic cells are used as the host cells, an expression vector for eukaryotic cells having a promoter, splicing site, poly(A) addition site and the like is used as the expression vector. Examples of such an expression vector include pKA1, pCDM8, pSVK3, pMSG, pSVL, pBK-CMV, pBK-RSV, the EBV vector, pRS, pcDNA3, pMSG and pYES2. In the same manner as described above, by incorporating DNA encoding the above-described polypeptide into such an expression vector and transforming eukaryotic host cells with the vector, followed by culturing the obtained transformant, the polypeptide encoded by the above-described DNA can be expressed in the eukaryotic host cells. In cases where pIND/V5-His, pFLAG-CMV-2, pEGFP-N1 or pEGFP-C1 was used as the expression vector, the above-described polypeptide can be expressed as a fusion protein having various added tags such as His tag, FLAG tag, myc tag, HA tag or GFP.

Introduction of the expression vector to the host cells can be carried out using a well-known method such as electroporation, the calcium phosphate method, the liposome method or the DEAE dextran method.

Isolation and purification of a polypeptide of interest from the host cells can be carried out by a combination of known separation operations. Examples of the operations include, but are not limited to, treatment by a denaturant such as urea or by a surfactant; ultrasonication treatment; enzyme digestion; salting-out and solvent fractional precipitation; dialysis; centrifugation; ultrafiltration; gel filtration; SDS-PAGE; isoelectric focusing; ion-exchange chromatography; hydrophobic chromatography; affinity chromatography; and reversed-phase chromatography.

The polypeptides obtained by the above method include, as mentioned above, those in the form of a fusion protein with another arbitrary protein. Examples thereof include fusion proteins with glutathion S-transferase (GST) and with a His tag. Such a polypeptide in the form of a fusion protein is also included within the scope of the present invention as the above-described polypeptide (c). Further, in some cases, a polypeptide expressed in a transformed cell is modified in various ways in the cell after translation thereof. Such a polypeptide having a post-translational modification is also included within the scope of the present invention as long as it has an immunity-inducing activity. Examples of such a post-translational modification include elimination of N-terminus methionine, N-terminus acetylation, glycosylation, limited degradation by an intracellular protease, myristoylation, isoprenylation and phosphorylation.

As described concretely in the following Examples, the above-described polypeptide having an immunity-inducing activity can cause regression of an already occurred tumor when administered to a cancer-bearing living body. Therefore, the immunity-inducing agent of the present invention can be used as a therapeutic and/or prophylactic agent for a cancer(s). In this case, cancers to be treated are those expressing the gene encoding the polypeptide of SEQ ID NO:2 or 4, and examples thereof include, but are not limited to, brain tumor; squamous cell carcinomas of head, neck, lung, uterus and esophagus; melanoma; adenocarcinomas of lung, breast and uterus; renal cancer; malignant mixed tumor; hepatocellular carcinoma; basal cell carcinoma; acanthomatous epulis; intraoral tumor; perianal adenocarcinoma; anal sac tumor; anal sac apocrine carcinoma; Sertoli cell tumor; vulva cancer; sebaceous adenocarcinoma; sebaceous epithelioma; sebaceous adenoma; sweat gland carcinoma; intranasal adenocarcinoma; nasal adenocarcinoma; thyroid cancer; colon cancer; bronchial adenocarcinoma; adenocarcinoma; ductal carcinoma; mammary adenocarcinoma; combined mammary adenocarcinoma; mammary gland malignant mixed tumor; intraductal papillary adenocarcinoma; fibrosarcoma; hemangiopericytoma; osteosarcoma; chondrosarcoma; soft tissue sarcoma; histiocytic sarcoma; myxosarcoma; undifferentiated sarcoma; lung cancer; mastocytoma; cutaneous leiomyoma; intra-abdominal leiomyoma; leiomyoma; chronic lymphocytic leukemia; lymphoma; gastrointestinal lymphoma; digestive organ lymphoma; small cell or medium cell lymphoma; adrenomedullary tumor; granulosa cell tumor; pheochromocytoma; bladder cancer (transitional cell carcinoma); suppurative inflammation; intra-abdominal liver tumor; liver cancer; plasmacytoma; malignant hemangiopericytoma; angiosarcoma; anal sac adenocarcinoma; oral cancer; metastatic malignant melanoma; amelanotic malignant melanoma; cutaneous malignant melanoma; malignant myoepithelioma; malignant seminoma; seminoma; adenocarcinoma of the large intestine; gastric adenocarcinoma; low-grade sebaceous carcinoma; ceruminous adenocarcinoma; apocrine carcinoma; poorly differentiated apocrine sweat gland carcinoma; malignant fibrous histiocytoma; multiple myeloma; mesenchymal malignant tumor; liposarcoma; osteosarcoma; sarcoma of unknown origin; soft part sarcoma (spindle cell tumor); poorly differentiated sarcoma; synovial sarcoma; angiosarcoma; metastatic malignant epithelioma; tubular mammary adenocarcinoma; mammary ductal carcinoma; inflammatory breast cancer; germinoma; leukemia; invasive trichoepithelioma; medium cell lymphoma; multicentric lymphoma; osteosarcoma (mammary gland); mastocytoma (Patnaik II type); mastocytoma (Grade II); and leiomyosarcoma. The animals to be treated are mammals, especially preferably humans, dogs and cats.

The administration route of the immunity-inducing agent of the present invention to a living body may be either oral administration or parenteral administration, and is preferably parenteral administration such as intramuscular administration, subcutaneous administration, intravenous administration or intraarterial administration. In cases where the immunity-inducing agent is used for therapy of a cancer, it may be administered to a regional lymph node in the vicinity of the tumor to be treated, as described in the Examples below, in order to enhance its anticancer activity. The dose may be any dose as long as the dose is effective for immune induction, and in cases where the agent is used for therapy and/or prophylaxis of a cancer, the dose may be one effective for therapy and/or prophylaxis of the cancer. The dose effective for therapy and/or prophylaxis of a cancer is appropriately selected depending on the size of the tumor, the symptom and the like, and usually, 0.0001 μg to 1000 μg, preferably 0.001 μg to 1000 μg of the agent in terms of the effective ingredient may be administered once or in several times per day per animal to be treated. The agent is preferably administered in several times, every several days to several months. As concretely shown in the Examples below, the immunity-inducing agent of the present invention can cause regression of an already occurred tumor. Therefore, since the agent can exert its anticancer activity also against a small number of cancer cells in the early stage, development or recurrence of the cancer can be prevented by using the agent before development of a cancer or after therapy for a cancer. That is, the immunity-inducing agent of the present invention is effective for both therapy and prophylaxis of a cancer.

The immunity-inducing agent of the present invention may contain only a polypeptide or may be formulated by mixing as appropriate with an additive such as a pharmaceutically acceptable carrier, diluent or vehicle suitable for each administration mode. Formulation methods and additives which may be used are well-known in the field of formulation of pharmaceuticals, and any of the methods and additives may be used. Specific examples of the additive include, but are not limited to, diluents such as physiological buffer solutions; vehicles such as sucrose, lactose, corn starch, calcium phosphate, sorbitol and glycine; binders such as syrup, gelatin, gum arabic, sorbitol, polyvinyl chloride and tragacanth; and lubricants such as magnesium stearate, polyethylene glycol, talc and silica. Examples of the formulation include oral preparations such as tablets, capsules, granules, powders and syrups; and parenteral preparations such as inhalants, injection solutions, suppositories and solutions. These formulations may be prepared by commonly known production methods.

The immunity-inducing agent of the present invention may be used in combination with an immunoenhancer capable of enhancing the immune response in a living body. The immunoenhancer may be contained in the immunity-inducing agent of the present invention or administered as a separate composition to a patient in combination with the immunity-inducing agent of the present invention.

Examples of the above-described immunoenhancer include adjuvants. Adjuvants can enhance the immune response by providing a reservoir of antigen (extracellularly or within macrophages), activating macrophages and stimulating specific sets of lymphocytes, thereby enhancing the anticancer activity. Therefore, especially in cases where the immunity-inducing agent of the present invention is used for therapy and/or prophylaxis of a cancer, the immunity-inducing agent preferably comprises an adjuvant, in addition to the above-described polypeptide as an effective ingredient. Many types of adjuvants are well-known in the art, and any of these adjuvants may be used. Specific examples of the adjuvants include MPL (SmithKline Beecham) and homologues of Salmonella minnesota Re 595 lipopolysaccharide obtained after purification and acid hydrolysis of the lipopolysaccharide; QS21 (SmithKline Beecham), pure QA-21 saponin purified from extract of Quillja saponaria; DQS21 described in WO96/33739 (SmithKline Beecham); QS-7, QS-17, QS-18 and QS-L1(So and 10 others, “Molecules and cells”, 1997, Vol. 7, p. 178-186); Freund's incomplete adjuvant; Freund's complete adjuvant; vitamin E; Montanide; alum; CpG oligonucleotides (see, for example, Kreig and 7 others, “Nature”, Vol. 374, p. 546-549); poly-I:C and derivatives thereof (e.g., poly ICLC); and various water in oil emulsions prepared from biodegradable oils such as squalene and/or tocopherol. Among these, Freund's incomplete adjuvant; Montanide; poly-I:C and derivatives thereof, and CpG oligonucleotides are preferred. The mixing ratio between the above-described adjuvant and polypeptide is typically about 1:10 to 10:1, preferably about 1:5 to 5:1, more preferably about 1:1. However, the adjuvant is not limited to the above-described examples, and adjuvants known in the art other than the above-described ones (for example, see Goding, “Monoclonal Antibodies: Principles and Practice”, 2nd edition, 1986) may be used when the immunity-inducing agent of the present invention is administered. Preparation methods for mixtures or emulsions of a polypeptide and an adjuvant are well-known to those skilled in the art of vaccination.

Further, in addition to the above-described adjuvants, factors that stimulate the immune response of the subject may be used as the above-described immunoenhancer. For example, various cytokines having a property to stimulate lymphocytes and/or antigen-presenting cells may be used as the immunoenhancer in combination with the immunity-inducing agent of the present invention. A number of such cytokines capable of enhancing the immune response are known to those skilled in the art, and examples thereof include, but are not limited to, interleukin-12 (IL-12), GM-CSF, IL-18, interferon-α, interferon-β, interferon-w, interferon-γ, and Flt3 ligand, which have been shown to promote the prophylactic action of vaccines. Such factors may also be used as the above-described immunoenhancer, and can be contained in the immunity-inducing agent of the present invention, or can be prepared as a separate composition to be administered to a patient in combination with the immunity-inducing agent of the present invention.

Further, by bringing the above-described polypeptide into contact with antigen-presenting cells in vitro, the antigen-presenting cells can be made to present the polypeptide. That is, the above-described polypeptides (a) to (c) can be used as agents for treating antigen-presenting cells. As the antigen-presenting cells, dendritic cells or B cells, which have MHC class I molecules, may preferably be employed. Various MHC class I molecules have been identified and well-known. MHC molecules in human are called HLA. Examples of HLA class I molecules include HLA-A, HLA-B and HLA-C, more specifically, HLA-A1, HLA-A0201, HLA-A0204, HLA-A0205, HLA-A0206, HLA-A0207, HLA-A11, HLA-A24, HLA-A31, HLA-A6801, HLA-B7, HLA-B8, HLA-B2705, HLA-B37, HLA-Cw0401 and HLA-Cw0602.

The dendritic cells or B cells having MHC class I molecules can be prepared from peripheral blood by a well-known method. For example, tumor-specific dendritic cells can be induced by inducing dendritic cells from bone marrow, umbilical cord blood or patient's peripheral blood using granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-3 (or IL-4), and then adding a tumor-related peptide to the culture system. By administering an effective amount of such dendritic cells, a response desired for therapy of a cancer can be induced. As the cells to be used, bone marrow or umbilical cord blood donated by a healthy individual, or bone marrow, peripheral blood or the like from the patient himself may be used. When autologous cells of the patient are used, high safety can be attained and serious side effects are expected to be avoided. The peripheral blood or bone marrow may be a fresh sample, cold-stored sample or frozen sample. As for the peripheral blood, whole blood may be cultured or the leukocyte components alone may be separated and cultured, and the latter is efficient and thus preferred. Further, among the leukocyte components, mononuclear cells may be separated. In cases where the cells are originated from bone marrow or umbilical cord blood, the whole cells constituting the bone marrow may be cultured, or mononuclear cells may be separated therefrom and cultured. Peripheral blood, the leukocyte components thereof and bone marrow cells contain mononuclear cells, hematopoietic stem cells and immature dendritic cells, from which dendritic cells are originated, and also CD4-positive cells and the like. As for the cytokine to be used, the production method thereof is not restricted and naturally-occurring or recombinant cytokine or the like may be employed as long as its safety and physiological activity have been confirmed. Preferably, a preparation with assured quality for medical use is used in a minimum necessary amount. The concentration of the cytokine(s) to be added is not restricted as long as the dendritic cells are induced, and usually, the total concentration of the cytokine(s) is preferably about 10 to 1000 ng/mL, more preferably about 20 to 500 ng/mL. The culture may be carried out using a well-known medium usually used for the culture of leukocytes. The culturing temperature is not restricted as long as the proliferation of the leukocytes is attained, and about 37° C. which is the body temperature of human is most preferred. The atmospheric environment during the culturing is not restricted as long as the proliferation of the leukocytes is attained, and to flow 5% CO₂ is preferred. The culturing period is not restricted as long as the necessary number of the cells is induced, and is usually 3 days to 2 weeks. As for the apparatuses used for separation and culturing of the cells, appropriate apparatuses, preferably those whose safety when applied to medical uses have been confirmed, and whose operations are stable and simple, may be employed. Particularly, as for the cell-culturing apparatus, not only the general vessels such as a Petri dish, flask and bottle, but also a layer type vessel, multistage vessel, roller bottle, spinner type bottle, bag type culturing vessel, hollow fiber column and the like may be used.

Bringing the above-described peptide of the present invention into contact with the antigen presenting cells in vitro may be carried out by a well-known method. For example, it may be carried out by culturing the antigen-presenting cells in a culture medium containing the above-described polypeptide. The concentration of the peptide in the medium is not restricted, and usually about 1 μg/ml to 100 μg/ml, preferably about 5 μg/ml to 20 μg/ml. The cell density during the culturing is not restricted and is usually about 10³ cells/ml to 10⁷ cells/ml, preferably about 5×10⁴ cells/ml to 5×10⁶ cells/ml. The culturing may be carried out according to a conventional method, and is preferably carried out at 37° C. under atmosphere of 5% CO₂. The maximum length of the peptide which can be presented on the surface of the antigen-presenting cells is usually about 30 amino acid residues. Therefore, in cases where the antigen-presenting cells are brought into contact with the polypeptide in vitro, the polypeptide may be prepared such that its length is not more than about 30 amino acid residues.

By culturing the antigen-presenting cells in the coexistence of the above-described polypeptide, the polypeptide is incorporated into MHC molecules of the antigen-presenting cells and presented on the surface of the antigen-presenting cells. Therefore, using the above-described polypeptide, isolated antigen-presenting cells containing the complex between the polypeptide and the MHC molecule can be prepared. Such antigen-presenting cells can present the polypeptide against T cells in vivo or in vitro, and induce, and allow proliferation of, cytotoxic T cells specific to the polypeptide.

By bringing the antigen-presenting cells prepared as described above having the complex between the above-described polypeptide and the MHC molecule into contact with T cells in vitro, cytotoxic T cells specific to the polypeptide can be induced and allowed to proliferate. This may be carried out by cocultivating the above-described antigen-presenting cells and T cells in a liquid medium. For example, it may be attained by suspending the antigen-presenting cells in a liquid medium, placing the suspension in vessels such as wells of a microplate, adding thereto T cells and then culturing the cells. The mixing ratio of the antigen-presenting cells to the T cells in the cocultivation is not restricted, and is usually about 1:1 to 1:100, preferably about 1:5 to 1:20 in terms of the number of cells. The density of the antigen-presenting cells suspended in the liquid medium is not restricted, and is usually about 100 to 10,000,000 cells/ml, preferably about 10,000 to 1,000,000 cells/ml. The cocultivation is preferably carried out at 37° C. under atmosphere of 5% CO₂ in accordance with a conventional method. The culturing time is not restricted, and is usually 2 days to 3 weeks, preferably about 4 days to 2 weeks. The cocultivation is preferably carried out in the presence of one or more interleukins such as IL-2, IL-6, IL-7 and IL-12. In this case, the concentration of IL-2 and IL-7 is usually about 5 U/ml to 20 U/ml, the concentration of IL-6 is usually about 500 U/ml to 2000 U/ml, and the concentration of IL-12 is usually about 5 ng/ml to 20 ng/ml, but the concentrations of the interleukins are not restricted thereto. The above-described cocultivation may be repeated once to several times adding fresh antigen-presenting cells. For example, the operation of discarding the culture supernatant after the cocultivation and adding a fresh suspension of antigen-presenting cells to further conduct the cocultivation may be repeated once to several times. The conditions of the each cocultivation may be the same as described above.

By the above-described cocultivation, cytotoxic T cells specific to the polypeptide are induced and allowed to proliferate. Thus, using the above-described polypeptide, isolated T cells can be prepared which selectively bind the complex between the polypeptide and the MHC molecule.

As described in the Examples below, the genes encoding the polypeptides of SEQ ID NOs:2, 16, 26, 28 and 39 and SEQ ID NOs:4, 18, 30 and 41 are expressed specifically in cancer cells and testis of dogs and humans, respectively. Thus, in cancer cells, significantly higher numbers of the polypeptides of SEQ ID NOs:2, 16, 26, 28 and 39 or SEQ ID NOs:4, 18, 30 and 41 exist than in normal cells. When cytotoxic T cells prepared as described above are administered to a living body while a part of the polypeptides existing in cancer cells are presented by MHC molecules on the surfaces of the cancer cells, the cytotoxic T cells can damage the cancer cells using the presented polypeptides as markers. Since antigen-presenting cells presenting the above-described polypeptides can induce, and allow proliferation of, cytotoxic T cells specific to the polypeptides also in vivo, cancer cells can be damaged also by administering the antigen-presenting cells to a living body. That is, the above-described cytotoxic T cells and the above-described antigen-presenting cells prepared using the above-described polypeptide are also effective as therapeutic and/or prophylactic agents for a cancer(s).

In cases where the above-described isolated antigen-presenting cells or isolated T cells are administered to a living body, these are preferably prepared by treating antigen presenting cells or T cells collected from the patient to be treated with the polypeptide (a) to (c) as described above in order to avoid the immune response in the living body that attacks these cells as foreign bodies.

The therapeutic and/or prophylactic agent for a cancer(s) comprising as an effective ingredient the antigen-presenting cells or T cells is preferably administered via a parenteral administration route such as intravenous or intraarterial administration. The dose is appropriately selected depending on the symptom, the purpose of administration and the like, and is usually 1 cell to 10,000,000,000,000 cells, preferably 1,000,000 cells to 1,000,000,000 cells, which dose is preferably administered once per several days to once per several months. The formulation may be, for example, the cells suspended in physiological buffered saline, and the formulation may be used in combination with another/other anticancer preparation(s) and/or cytokine(s). Further, one or more additives well-known in the field of formulation of pharmaceuticals may also be added.

Also by expression of the polynucleotide encoding the above-described polypeptide (a) to (c) in the body of the animal to be treated, antibody production and cytotoxic T cells can be induced in the living body, and an effect comparable to the administration of a polypeptide can be obtained. That is, the immunity-inducing agent of the present invention may be one comprising as an effective ingredient a recombinant vector having a polynucleotide encoding the above-described polynucleotide (a) to (c), which recombinant vector is capable of expressing the polypeptide in a living body. Such a recombinant vector capable of expressing an antigenic polypeptide is also called gene vaccine. The vector used for production of a gene vaccine is not restricted as long as it is a vector capable of expressing a polypeptide in cells of the animal to be treated (preferably in a mammalian cell), and may be either a plasmid vector or a virus vector, and any known vector in the field of gene vaccines may be used. The polynucleotide such as DNA or RNA encoding the above-described polypeptide can be easily prepared, as mentioned above, by a conventional method. Incorporation of the polynucleotide into a vector can be carried out using a method well-known to those skilled in the art.

The administration route of the gene vaccine is preferably a parenteral route such as intramuscular, subcutaneous, intravenous or intraarterial administration, and the dose may be appropriately selected depending on the type of the antigen and the like, and usually about 0.1 μg to 100 mg, preferably about 1 μg to 10 mg in terms of the weight of the gene vaccine per 1 kg of body weight.

Methods using a virus vector include those wherein a polynucleotide encoding the above-described polypeptide is incorporated into an RNA virus or DNA virus such as retrovirus, adenovirus, adeno-associated virus, herpes virus, vaccinia virus, pox virus, poliovirus or Sindbis virus, and then the animal to be treated is infected by the resulting virus. Among these methods, those using retrovirus, adenovirus, adeno-associated virus, vaccinia virus or the like are especially preferred.

Other methods include a method wherein an expression plasmid is directly intramuscularly administered (DNA vaccine method), the liposome method, lipofectin method, microinjection method, calcium phosphate method, electroporation method and the like, and the DNA vaccine method and liposome method are especially preferred.

Methods for actually making the gene encoding the above-described polypeptide of the present invention act as a pharmaceutical include the in vivo method wherein the gene is directly introduced into the body, and the ex vivo method wherein a kind of cells are collected from the animal to be treated, the gene is introduced into the cells ex vivo, and then the cells are returned to the body (Nikkei Science, 1994, April, p. 20-45; The Pharmaceutical Monthly, 1994, Vol. 36, No. 1, p. 23-48; Experimental Medicine, Extra Edition, 1994, Vol. 12, No. 15; and references cited in these papers and the like). The in vivo method is more preferred.

In cases where the gene is administered by the in vivo method, the gene may be administered through an appropriate administration route depending on the disease to be treated, symptom and so on. It may be administered, for example, by intravenous, intraarterial, subcutaneous, intramuscular administration or the like. In cases where the gene is administered by the in vivo method, the gene may be formulated into a preparation such as a solution, and in general, it is formulated into an injection solution or the like containing the DNA encoding the above-described peptide of the present invention as an effective ingredient. A commonly used carrier(s) may be added as required. In the case of a liposome or membrane fusion liposome (Sendai virus (HVJ)-liposome or the like) containing the DNA, the liposome may be formulated into a liposome preparation such as a suspension, frozen preparation or centrifugally concentrated frozen preparation.

In the present invention, “the base sequence shown in SEQ ID NO:1” includes not only the base sequence expressly written in SEQ ID NO:1, but also the sequence complementary thereto. Thus, “a polynucleotide having the base sequence shown in SEQ ID NO:1” includes a single-stranded polynucleotide having the base sequence expressly written in SEQ ID NO:1, a single-stranded polynucleotide having the base sequence complementary thereto, and a double-stranded polynucleotide composed of these single strand polynucleotides. When the polynucleotide encoding the polypeptide used in the present invention is prepared, any one of these base sequences should be appropriately selected, and those skilled in the art can easily carry out the selection.

EXAMPLES

The present invention will now be described more concretely by way of Examples.

Example A-1 Acquisition of Novel Cancer Antigen Protein by SEREX Method

(1) Preparation of cDNA Library

Total RNA was prepared from testis tissue of a healthy dog by the Acid guanidium-Phenol-Chloroform method, and poly(A) RNA was purified using Oligotex-dT30 mRNA purification Kit (manufactured by Takara Shuzo Co., Ltd.) in accordance with the protocol attached to the kit.

Using the obtained mRNA (5 μg), a dog testis cDNA phage library was synthesized. Preparation of the cDNA phage library was carried out using cDNA Synthesis Kit, ZAP-cDNA Synthesis Kit, and ZAP-cDNA Gigapack III Gold Cloning Kit (manufactured by STRATAGENE) in accordance with the protocols attached to the kits. The size of the prepared cDNA phage library was 1.3×10⁶ pfu/ml.

(2) Screening of cDNA Library with Serum

Using the dog testis-derived cDNA phage library prepared as described above, immunoscreening was carried out. More particularly, host E. coli cells (XL1-Blue MRF′) were infected with the library such that 2,340 clones should appear on an NZY agarose plate having the size of Φ90×15 mm, and cultured at 42° C. for 3 to 4 hours to allow the phage to form plaques. The plate was covered with nitrocellulose membrane (Hybond C Extra: manufactured by GE Healthcare Bio-Science) impregnated with IPTG (isopropyl-β-D-thiogalactoside) at 37° C. for 4 hours to induce and express proteins, which were thus transferred to the membrane. Subsequently, the membrane was recovered and soaked in TBS (10 mM Tris-HCl, 150 mM NaCl; pH 7.5) containing 0.5% non-fat dry milk, followed by shaking it at 4° C. overnight to suppress non-specific reactions. This filter was allowed to react with 500-fold diluted canine patient serum at room temperature for 2 to 3 hours.

As the above-described canine patient serum, serum collected from canine patients suffering from squamous cell carcinoma was used. The serum was stored at −80° C. and pretreated immediately before use. The method of the pretreatment of the serum was as follows. That is, host E. coli cells (XL1-Blue MRF′) were infected with λ ZAP Express phage to which no foreign gene was inserted, and then cultured on NZY plate medium at 37° C. overnight. Subsequently, the buffer of 0.2 M NaHCO₃, pH 8.3 containing 0.5 M NaCl was added to the plate, and the plate was left to stand at 4° C. for 15 hours, followed by collecting the supernatant as an E. coli/phage extract. Thereafter, the collected E. coli/phage extract was allowed to flow through an NHS column (manufactured by GE Healthcare Bio-Science) to immobilize proteins derived from the E. coli/phage thereon. The serum from the canine patients was allowed to flow through and react with this protein-immobilized column to remove antibodies adsorbed on E. coli and/or the phage. The serum fraction that passed through the column was 500-fold diluted with TBS containing 0.5% non-fat dry milk, and the resulting diluent was used as the material for the immunoscreening.

The membrane on which the thus treated serum and the above-described fusion protein were blotted was washed 4 times with TBS-T (0.05% Tween 20/TBS), and allowed to react with goat anti-dog IgG (Goat anti Dog IgG-h+I HRP conjugated: manufactured by BETHYL Laboratories) 5000-fold diluted with TBS containing 0.5% non-fat dry milk as a secondary antibody at room temperature for 1 hour, followed by detection by the enzyme coloring reaction using the NBT/BCIP reaction solution (manufactured by Roche). Colonies at positions where a positive coloring reaction was observed were recovered from the NZY agarose plate having the size of Φ90×15 mm, and dissolved in 500 μl of SM buffer (100 mM NaCl, 10 mM MgClSO₄, 50 mM Tris-HCl, 0.01% gelatin; pH 7.5). The screening was repeated as a second and third screening in the same manner as described above until a single coloring reaction-positive colony was obtained, thereby isolating one positive clone after screening of 30,940 phage clones reactive with IgG in the serum.

(3) Homology Search of Isolated Antigen Gene

To subject the single positive clone isolated by the above-described method to a base sequence analysis, an operation of conversion of the phage vector to a plasmid vector was carried out. More particularly, 200 μl of a solution prepared to contain a host E. coli (XL1-Blue MRF′) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 100 μl of a purified phage solution and further with 1 μl of ExAssist helper phage (manufactured by STRATAGENE), and the reaction was allowed to proceed at 37° C. for 15 minutes. To the reaction mixture, 3 ml of LB medium was added, and the mixture was cultured at 37° C. for 2.5 to 3 hours, followed by immediate incubation in a water bath at 70° C. for 20 minutes. The mixture was then centrifuged at 4° C. at 1000×g for 15 minutes, and the supernatant was recovered as a phagemid solution. Subsequently, 200 μl of a solution prepared to contain a phagemid host E. coli (SOLR) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 10 μl of a purified phage solution, and the reaction was allowed to proceed at 37° C. for 15 minutes. Thereafter, 50 μl of the reaction mixture was plated on ampicillin (final concentration: 50 μg/ml)-containing LB agar medium, and cultured at 37° C. overnight. A single colony of transformed SOLR was recovered and cultured in ampicillin (final concentration: 50 μg/ml)-containing LB medium at 37° C., followed by purification of plasmid DNA having an insert of interest using QIAGEN plasmid Miniprep Kit (manufactured by Qiagen).

The purified plasmid was subjected to an analysis of the entire sequence of the insert by the primer walking method using the T3 primer described in SEQ ID NO:5 and the T7 primer described in SEQ ID NO:6. By this sequence analysis, the gene sequence described in SEQ ID NO:1 was obtained. Using the base sequence and the amino acid sequence of this gene, homology search against known genes was carried out using a homology search program BLAST (http://www.ncbi.nlm.nih.gov/BLAST/). As a result, it was revealed that the obtained gene is the gene (Accession No. XM_535343) encoding a protein (Accession No.XP_535343) whose function is unknown. The human homologous factor of this gene was the gene (Accession No.NM_152660) encoding a protein (Accession No.NP_689873) whose function is also unknown (homology: base sequence, 93%; amino acid sequence, 99%). The base sequence of the human homologous factor is shown in SEQ ID NO:3, and the amino acid sequence thereof is shown in SEQ ID NO:4.

(4) Analysis of Expression in Each Tissue

The expression of the gene, which was obtained by the above-described method, in normal tissues and various cell lines of dog and human were investigated by the RT-PCR (Reverse Transcription-PCR) method. The reverse transcription reaction was carried out as follows. That is, total RNA was extracted from 50 to 100 mg of each tissue or 5 to 10×10⁶ cells of each cell line using TRIZOL reagent (manufactured by Invitrogen) in accordance with the protocol attached to the kit. Using this total RNA, cDNA was synthesized by Superscript First-Strand Synthesis System for RT-PCR (manufactured by Invitrogen) in accordance with the protocol attached to the kit. As the cDNAs from human normal tissues (brain, hippocampus, testis, colon and placenta), Gene Pool cDNA (manufactured by Invitrogen), QUICK-Clone cDNA (manufactured by CLONTECH) and Large-Insert cDNA Library (manufactured by CLONTECH) were used. The PCR reactions were carried out as follows using primers (described in SEQ ID NOs:7 and 8) specific to the obtained canine gene and its human homologous gene. That is, respective reagents and the attached buffer were mixed such that the mixture should contain 0.25 μl of the sample prepared by the reverse transcription reaction, 2 μM each of the above primers, 0.2 mM each of dNTP and 0.65 U of ExTaq polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 25 μl, and the reaction was carried out with 30 cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 1 minute using Thermal Cycler (manufactured by BIO RAD). The gene-specific primers having the base sequences shown in the above-described SEQ ID NOs:7 and 8 were those which amplify the regions of the 87th to 606th bases of the base sequence of SEQ ID NO:1 and the 173rd to 695th bases of the base sequence of SEQ ID NO:3, and can be used for investigation of the expression of both the canine gene and its human homologous gene. As a control for comparison, primers (described in SEQ ID NOs:9 and 10) specific to GAPDH were used simultaneously. As a result, as shown in FIG. 1, strong expression of the obtained canine gene was observed in testis among the normal dog tissues, and on the other hand, strong expression was observed in the canine breast cancer cell line. Expression of the human homologous gene was confirmed, as is the case with the canine gene, only in testis among the human normal tissues, but the expression was detected in brain tumor, leukemia, breast cancer and lung cancer cells among human cancer cell lines. Thus, the human homologous gene was also confirmed to be specifically expressed in testis and cancer cells.

In FIG. 1, reference numeral 1 in the ordinate indicates the expression pattern of the above identified gene, and reference numeral 2 indicates the expression pattern of the GAPDH gene as a control for comparison.

Example A-2 Preparation of Novel Cancer Antigen Proteins (1) Preparation of Recombinant Protein

Based on the gene of SEQ ID NO:1 obtained in Example A-1, a recombinant protein was prepared by the following method. Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the vector which was prepared from the phagemid solution obtained in Example A-1 and was subjected to the sequence analysis, 0.4 μM each of two kinds of primers having NdeI and XhoI restriction sites (described in SEQ ID NOs:11 and 12), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 15 seconds and 72° C. for 1 minute using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:2. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 930 bp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes NdeI and XhoI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET16b (manufactured by Novagen) that had been treated with NdeI and XhoI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG.

On the other hand, based on the gene of SEQ ID NO: 3, a recombinant protein of the human homologous gene was prepared by the following method. Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the cDNA prepared in Example A-1 whose expression could be confirmed by the RT-PCR method in various tissues/cells, 0.4 μM each of two kinds of primers having EcoRV and EcoRI restriction sites (described in SEQ ID NOs:13 and 14), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 15 seconds and 72° C. for 1 minute using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:4. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 930 bp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes EcoRV and EcoRI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30a (manufactured by Novagen) that had been treated with EcoRV and EcoRI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG.

(2) Purification of Recombinant Protein

The above-obtained recombinant E. coli cells that expressed SEQ ID NO:1 and SEQ ID NO:3, respectively, were cultured in 100 μg/ml ampicillin-containing LB medium at 37° C. until the absorbance at 600 nm reached about 0.7, and then isopropyl-3-D-1-thiogalactopyranoside was added thereto such that its final concentration should be 1 mM, followed by culturing them at 37° C. for 4 hours. Subsequently, the cells were collected by centrifugation at 4,800 rpm for 10 minutes. The pellet of the cells was suspended in phosphate-buffered saline and further subjected to centrifugation at 4,800 rpm for 10 minutes to wash the cells.

The cells were suspended in 50 mM Tris-HCl buffer (pH 8.0) and subjected to sonication on ice. The sonicated solution of E. coli was centrifuged at 6,000 rpm for 20 minutes to obtain the supernatant as the soluble fraction and the precipitate as the insoluble fraction.

The insoluble fraction was suspended in 50 mM Tris-HCl buffer (pH 8.0) and centrifuged at 6,000 rpm for 15 minutes. This operation was repeated twice and an operation of removal of proteases was carried out.

The residue was suspended in 6M guanidine hydrochloride, 0.15 M sodium chloride-containing 50 mM Tris-HCl buffer (pH 8.0), and the resulting suspension was left to stand at 4° C. for 20 hours to denature proteins. Thereafter, the suspension was centrifuged at 6,000 rpm for 30 minutes, and the obtained soluble fraction was placed in a nickel chelate column prepared by a conventional method (carrier: Chelating Sepharose (trademark) Fast Flow (GE Health Care); column volume: 5 mL; equilibration buffer: 6M guanidine hydrochloride, 0.15 M sodium chloride-containing 50 mM Tris-HCl buffer (pH 8.0)), followed by leaving it to stand at 4° C. overnight to allow adsorption to the nickel-chelated carrier. The supernatant was recovered by centrifugation of this column carrier at 1,500 rpm for 5 minutes, and the column carrier was suspended in phosphate-buffered saline, followed by refilling the column with the resulting suspension.

The fraction that was not adsorbed to the column was washed away with 10 column volumes of 0.5 M sodium chloride-containing 0.1 M acetate buffer (pH 4.0), and elution was immediately carried out with 0.5 M sodium chloride-containing 0.1 M acetate buffer (pH 3.0) to obtain a purified fraction, which was used as the material for administration tests thereafter. The proteins of interest in respective eluted fractions were confirmed by Coomassie staining carried out according to a conventional method. Among these, the canine protein of interest is shown in FIG. 2.

The buffer contained in the purified preparation obtained by the above-described method was replaced with a reaction buffer (50 mM Tris-HCl, 100 mM NaCl, 5 mM CaCl₂; pH8.0), and cleavage of His tag by Factor Xa protease and purification of the protein of interest were carried out, using FactorXa Cleavage Capture Kit (manufactured by Novagen), in accordance with the protocols attached to the kit. Subsequently, the buffer contained in 1.2 ml of the purified preparation obtained by the above-described method was replaced with physiological phosphate buffer (manufactured by Nissui Pharmaceutical) by ultrafiltration using NANOSEP 10K OMEGA (manufactured by PALL), and the resulting solution was filtered aseptically using HT Tuffryn Acrodisc 0.22 μm (manufactured by PALL) and used in the following experiments.

Example A-3 Test of Administration of Recombinant Protein to Cancer-Bearing Dogs (1) Antitumor Assay

The anti-tumor effect of the two kinds of recombinant proteins which were purified as described above was assessed in two individuals of cancer-bearing dogs having epidermal tumor (2 individuals having mammary gland tumor).

An equal amount of Freund's incomplete adjuvant (manufactured by Wako Pure Chemicals) was mixed with 100 μg (0.5 ml) of the recombinant polypeptides (derived from dog and human), respectively, to prepare two kinds of therapeutic agents for a cancer(s). Each of these agents was administered to a regional lymph node in the vicinity of the tumor a total of 3 times, by carrying out the subsequent administrations 3 days and 7 days after the first administration. As a result, the tumors with a size of about 25 mm³ and 50 mm³ at the time of administration of the therapeutic agents for a cancer(s) (derived from dog and human), respectively, were reduced in size to 20 mm³ and 42 mm³, respectively, 10 days after the first administration; 13 mm³ and 26 mm³, respectively, 20 days after the first administration; and to 5 mm³ and 10 mm³, respectively, 30 days after the first administration.

Further, to a canine patient suffering from malignant melanoma, a mixture of 100 μg (0.5 ml) of the above-described polypeptide derived from dog and 0.5 ml of Freund's incomplete adjuvant was administered intracutaneously at the periphery of the tumor a total of 3 times at the same intervals as described above. Further, concurrently with the respective administrations, 10 MU of “Intercat” which is a recombinant feline interferon was administered subcutaneously. As a result, the tumor with a size of about 142 mm³ at the time of administration of the therapeutic agent for a cancer(s) completely regressed 29 days after the first administration.

Further, to a canine patient suffering from nasal adenocarcinoma, a mixture of 100 μg (0.5 ml) of the above-described polypeptide derived from dog and 0.5 ml of Freund's incomplete adjuvant was administered in the same manner as described above a total of 3 times. Further, concurrently with the respective administrations, 100 μg of canine interleukin 12 was administered subcutaneously. As a result, the tumor with a size of about 57 mm³ at the time of administration of the therapeutic agent for a cancer(s) completely regressed 14 days after the first administration.

(2) Immune Inducibility Assay

Blood from the canine patient in which the anti-tumor effect was obtained in the administration test in the above-described (1) was collected before administration of the therapeutic agent for a cancer(s), and 10 days and 30 days after the first administration. Peripheral blood mononuclear cells were isolated according to a conventional method, and by the ELISPOT assay for IFNγ using it, the immune inducibility of each administered recombinant protein was assayed.

In a 96-well plate manufactured by Millipore (MultiScreen-IP, MAIPS 4510), 100 μL/well of 70% ethanol was placed and the plate was left to stand for 5 minutes, followed by removal of the ethanol by aspiration. The plate was washed with sterile water and 300 μl/well of 200 mM Sodium Bicarbonate (pH8.2) was placed therein. After leaving it to stand for 5 minutes, Sodium Bicarbonate was removed by aspiration, and then the plate was washed. Subsequently, 0.5 μl/well of anti-canine interferon γ monoclonal antibody (manufactured by R&D, clone 142529, MAB781) mixed with 200 mM Sodium Bicarbonate was placed in wells, and the plate was incubated at 37° C. overnight to immobilize the primary antibody. After removal of the primary antibody by aspiration, 300 μL/well of a blocking solution (1% BSA-5% sucrose-200 mM Sodium Bicarbonate (pH8.2)) was added to the wells, and the plate was incubated at 4° C. overnight to block the plate. After removal of the blocking solution by aspiration, 300 μL/well of 10% fetal calf serum-containing RPMI medium (manufactured by Invitrogen) was placed in the wells, and the plate was left to stand for 5 minutes, followed by removal of the medium by aspiration. Subsequently, 5×10⁵ cells/well of the canine peripheral blood mononuclear cells suspended in 10% fetal calf serum-containing RPMI medium were placed in the plate, and 10 μL/well of the canine-derived polypeptide or human-derived polypeptide used in each administration was added thereto, followed by culturing the cells under the conditions of 37° C. and 5% CO₂ for 24 hours, to allow immunocytes that might exist in the peripheral blood mononuclear cells to produce interferon γ. After the culture, the medium was removed, and the wells were washed 6 times with a washing solution (0.1% Tween20-200 mM Sodium Bicarbonate (pH8.2)). In each well, 100 μL of rabbit anti-dog polyclonal antibody 1000-fold diluted with the above-described blocking solution was placed, and the plate was incubated at 4° C. overnight. After washing the wells 3 times with the above-described washing solution, 100 μL of HRP-labeled anti-rabbit antibody 1000-fold diluted with the above-described blocking solution was placed in each well, and the reaction was allowed to proceed at 37° C. for 2 hours. After washing the wells 3 times with the above-described washing solution, the resultant was colored with Konica Immunostain (manufactured by Konica), and the wells were washed with water to stop the reaction. Thereafter, the membrane was dried, and the number of the appeared spots was counted using KS ELISPOT (manufactured by Carl Zeiss, Inc.).

As a result, in either canine patient to which the canine polypeptide or the human polypeptide was administered, peripheral blood mononuclear cells sampled before the administration of the polypeptide showed no spots. On the other hand, in the canine patient to which the canine polypeptide was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 20 and 36 spots, respectively. In the canine patient to which the human polypeptide was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 24 and 36 spots, respectively.

From the above results, it is confirmed that immunocytes which specifically react with the administered recombinant protein and produce interferon γ were induced in all of the canine patients to which the recombinant protein was administered, and it is thought that the anti-tumor effect described in (1) was exerted by immunoreactions in which these immunocytes are mainly involved.

Example B-1 Acquisition of Novel Cancer Antigen Protein by SEREX Method

(1) Preparation of cDNA Library

Total RNA was prepared from testis tissue of a healthy dog by the Acid guanidium-Phenol-Chloroform method, and poly(A) RNA was purified using Oligotex-dT30 mRNA purification Kit (manufactured by Takara Shuzo Co., Ltd.) in accordance with the protocol attached to the kit.

Using the obtained mRNA (5 μg), a dog testis cDNA phage library was synthesized. Preparation of the cDNA phage library was carried out using cDNA Synthesis Kit, ZAP-cDNA Synthesis Kit, and ZAP-cDNA Gigapack III Gold Cloning Kit (manufactured by STRATAGENE) in accordance with the protocols attached to the kits. The size of the prepared cDNA phage library was 1.3×10⁶ pfu/ml.

(2) Screening of cDNA Library with Serum

Using the dog testis-derived cDNA phage library prepared as described above, immunoscreening was carried out. More particularly, host E. coli cells (XL1-Blue MRF′) were infected with the library such that 2,340 clones should appear on an NZY agarose plate having the size of Φ90×15 mm, and cultured at 42° C. for 3 to 4 hours to allow the phage to form plaques. The plate was covered with nitrocellulose membrane (Hybond C Extra: manufactured by GE Healthcare Bio-Science) impregnated with IPTG (isopropyl-β-D-thiogalactoside) at 37° C. for 4 hours to induce and express proteins, which were thus transferred to the membrane. Subsequently, the membrane was recovered and soaked in TBS (10 mM Tris-HCl, 150 mM NaCl; pH 7.5) containing 0.5% non-fat dry milk, followed by shaking at 4° C. overnight to suppress non-specific reactions. This filter was allowed to react with 500-fold diluted canine patient serum at room temperature for 2 to 3 hours.

As the above-described canine patient serum, serum collected from canine patients suffering from tumor proximal to the anus was used. The serum was stored at −80° C. and pretreated immediately before use. The method of the pretreatment of the serum was as follows. That is, host E. coli cells (XL1-Blue MRF′) were infected with λ ZAP Express phage to which no foreign gene was inserted, and then cultured on NZY plate medium at 37° C. overnight. Subsequently, the buffer of 0.2 M NaHCO₃, pH 8.3 containing 0.5 M NaCl was added to the plate, and the plate was left to stand at 4° C. for 15 hours, followed by collecting the supernatant as an E. coli/phage extract. Thereafter, the collected E. coli/phage extract was allowed to flow through an NHS column (manufactured by GE Healthcare Bio-Science) to immobilize proteins derived from the E. coli/phage thereon. The serum from the canine patients was allowed to flow through and react with this protein-immobilized column to remove antibodies adsorbed on E. coli and/or the phage. The serum fraction that passed through the column was 500-fold diluted with TBS containing 0.5% non-fat dry milk, and the resulting diluent was used as the material for the immunoscreening.

The membrane on which the thus treated serum and the above-described fusion protein were blotted was washed 4 times with TBS-T (0.05% Tween 20/TBS), and allowed to react with goat anti-dog IgG (Goat anti Dog IgG-h+I HRP conjugated: manufactured by BETHYL Laboratories) 5000-fold diluted with TBS containing 0.5% non-fat dry milk as a secondary antibody at room temperature for 1 hour, followed by detection by the enzyme coloring reaction using the NBT/BCIP reaction solution (manufactured by Roche). Colonies at positions where a positive coloring reaction was observed were recovered from the NZY agarose plate having the size of Φ90×15 mm, and dissolved in 500 μl of SM buffer (100 mM NaCl, 10 mM MgClSO₄, 50 mM Tris-HCl, 0.01% gelatin; pH 7.5). The screening was repeated as a second and third screening in the same manner as described above until a single coloring reaction-positive colony was obtained, thereby isolating one positive clone after screening of 30,940 phage clones reactive with IgG in the serum.

(3) Homology Search of Isolated Antigen Gene

To subject the single positive clone isolated by the above-described method to a base sequence analysis, an operation of conversion of the phage vector to a plasmid vector was carried out. More particularly, 200 μl of a solution prepared to contain a host E. coli (XL1-Blue MRF′) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 100 μl of a purified phage solution and further with 1 μl of ExAssist helper phage (manufactured by STRATAGENE), and the reaction was allowed to proceed at 37° C. for 15 minutes. To the reaction mixture, 3 ml of LB medium was added, and the mixture was cultured at 37° C. for 2.5 to 3 hours, followed by immediate incubation in a water bath at 70° C. for 20 minutes. The mixture was then centrifuged at 4° C. at 1000×g for 15 minutes, and the supernatant was recovered as a phagemid solution. Subsequently, 200 μl of a solution prepared to contain a phagemid host E. coli (SOLR) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 10 μl of a purified phage solution, and the reaction was allowed to proceed at 37° C. for 15 minutes. Thereafter, 50 μl of the reaction mixture was plated on ampicillin (final concentration: 50 μg/ml)-containing LB agar medium, and cultured at 37° C. overnight. A single colony of transformed SOLR was recovered and cultured in ampicillin (final concentration: 50 μg/ml)-containing LB medium at 37° C., followed by purification of plasmid DNA having an insert of interest using QIAGEN plasmid Miniprep Kit (manufactured by Qiagen).

The purified plasmid was subjected to an analysis of the entire sequence of the insert by the primer walking method using the T3 primer described in SEQ ID NO:5 and the T7 primer described in SEQ ID NO:6. By this sequence analysis, the gene sequence described in SEQ ID NO:15 was obtained. Using the base sequence and the amino acid sequence of this gene, homology search against known genes was carried out using a homology search program BLAST (http://www.ncbi.nlm.nih.gov/BLAST/). As a result, it was revealed that the obtained gene is the calmegin gene. The human homologous factor of the canine calmegin gene was human calmegin (homology: base sequence, 90%; amino acid sequence, 89%). The base sequence of human calmegin is shown in SEQ ID NO:17, and the amino acid sequence thereof is shown in SEQ ID NO:18.

(4) Analysis of Expression in Each Tissue

The expression of the gene, which was obtained by the above-described method, in normal tissues and various cell lines of dog and human were investigated by the RT-PCR (Reverse Transcription-PCR) method. The reverse transcription reaction was carried out as follows. That is, total RNA was extracted from 50 to 100 mg of each tissue or 5 to 10×10⁶ cells of each cell line using TRIZOL reagent (manufactured by Invitrogen) in accordance with the protocol attached to the kit. Using this total RNA, cDNA was synthesized by Superscript First-Strand Synthesis System for RT-PCR (manufactured by Invitrogen) in accordance with the protocol attached to the kit. As the cDNAs from human normal tissues (brain, hippocampus, testis, colon and placenta), Gene Pool cDNA (manufactured by Invitrogen), QUICK-Clone cDNA (manufactured by CLONTECH) and Large-Insert cDNA Library (manufactured by CLONTECH) were used. The PCR reactions were carried out as follows using primers (described in SEQ ID NOs:19 and 20) specific to the obtained gene. That is, respective reagents and the attached buffer were mixed such that the mixture should contain 0.25 μl of the sample prepared by the reverse transcription reaction, 2 μM each of the above primers, 0.2 mM each of dNTP and 0.65 U of ExTaq polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 25 and the reaction was carried out with 30 cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 1 minute using Thermal Cycler (manufactured by BIO RAD). The above-described gene-specific primers were those which amplify the regions of the 755th to 1318th bases of the base sequence of SEQ ID NO:15 (canine calmegin gene) and the 795th to 1358th bases of the base sequence of SEQ ID NO:17 (human calmegin gene), and can be used for investigation of the expression of both the canine calmegin gene and the human calmegin gene. As a control for comparison, primers (described in SEQ ID NOs:9 and 10) specific to GAPDH were used simultaneously. As a result, as shown in FIG. 3, strong expression of the canine calmegin gene was observed in testis among the normal dog tissues, and on the other hand, strong expression was observed in canine tumor cell lines. Expression of the human calmegin gene was confirmed, as is the case with the canine calmegin gene, only in testis among the human normal tissues, but the expression was detected in brain tumor, leukemia and esophagus cancer cells among human cancer cell lines. Thus, the human calmegin gene was also confirmed to be specifically expressed in testis and cancer cells.

In FIG. 3, reference numeral 1 in the ordinate indicates the expression pattern of the calmegin gene, and reference numeral 2 indicates the expression pattern of the GAPDH gene as a control for comparison.

Example B-2 Preparation of Canine and Human Calmegin Proteins (1) Preparation of Recombinant Protein

Based on the gene of SEQ ID NO:15 obtained in Example B-1, a recombinant protein was prepared by the following method. Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the vector that was prepared from the phagemid solution obtained in Example B-1 and was subjected to the sequence analysis, 0.4 μM each of two kinds of primers having BamHI and EcoRI restriction sites (described in SEQ ID NOs:21 and 22), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 15 seconds and 72° C. for 2 minutes using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:16. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 1.9 kbp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes BamHI and EcoRI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30a (manufactured by Novagen) that had been treated with BamHI and EcoRI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG.

On the other hand, based on the gene of SEQ ID NO:17, a recombinant protein of the human homologous gene was prepared by the following method. Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the cDNA prepared in Example B-1 whose expression could be confirmed by the RT-PCR method in various tissues/cells, 0.4 μM each of two kinds of primers having EcoRI and XhoI restriction sites (described in SEQ ID NOs:23 and 24), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 15 seconds and 72° C. for 2 minutes using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:18. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 1.9 kbp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes EcoRI and XhoI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30a (manufactured by Novagen) that had been treated with EcoRI and XhoI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG.

(2) Purification of Recombinant Protein

The above-obtained recombinant E. coli cells that expressed SEQ ID NO:15 and SEQ ID NO:17, respectively, were cultured in 30 μg/ml kanamycin-containing LB medium at 37° C. until the absorbance at 600 nm reached about 0.7, and then isopropyl-3-D-1-thiogalactopyranoside was added thereto such that its final concentration should be 1 mM, followed by culturing them at 37° C. for 4 hours. Subsequently, the cells were collected by centrifugation at 4,800 rpm for 10 minutes. The pellet of the cells was suspended in phosphate-buffered saline and further subjected to centrifugation at 4,800 rpm for 10 minutes to wash the cells.

The obtained pellet of E. coli cells was suspended in 20 mM phosphate buffer (pH 7.0) and subjected to sonication on ice. The sonicated solution of E. coli was centrifuged at 6,000 rpm for 20 minutes to obtain the supernatant as the soluble fraction and the precipitate as the insoluble fraction.

The soluble fraction was placed in an ion-exchange column (carrier: SP Sepharose (trademark) Fast Flow (GE Health Care); column volume: 5 mL; equilibration buffer: 20 mM phosphate buffer (pH 7.0)). The column was washed with 10 column volumes of 20 mM phosphate buffer (pH 7.0), and elution was carried out with density gradient of salt by 0.3 M-1.0 M sodium chloride-containing 20 mM phosphate buffer (pH 7.0). Six column volumes of the eluted fraction was collected in each elution step.

Among these eluted fractions, the 1st to 6th fractions eluted with 0.3 M sodium chloride-containing 20 mM phosphate buffer (pH 7.0) and the 1st fraction eluted with 1.0 M sodium chloride-containing 20 mM phosphate buffer (pH 7.0) were combined, and the resulting solution was subjected to additional purification by a secondary column.

For the secondary column, a column carrier Bio gel HT Type II (BioRad) was used. The column volume was 5 mL. The column was equilibrated with 10 column volumes of 0.3 M sodium chloride-containing 20 mM phosphate buffer (pH 7.0), and the above-described eluted fractions were placed in the column. The fractions that were not adsorbed to the column was washed away with 10 column volumes of 0.3 M sodium chloride-containing 20 mM phosphate buffer (pH 7.0) and 0.1 M phosphate buffer (pH 7.0), and elution was carried out with 0.2 M phosphate buffer (pH 7.0) to obtain a purified fraction, which was used as the material for administration tests thereafter. The proteins of interest in the eluted fractions were confirmed by Coomassie staining carried out according to a conventional method. Among these, the canine calmegin protein is shown in FIG. 4.

To 1 ml of a reaction buffer (20 mM Tris-HCl, 50 mM NaCl, 2 mM CaCl₂; pH 7.4), 200 μl of the purified preparation obtained by the above-described method was aliquoted, and 2 μl of enterokinase (manufactured by Novagen) was then added thereto, followed by leaving it to stand at room temperature overnight to cleave His tag. The resulting product was purified using Enterokinase Cleavage Capture Kit (manufactured by Novagen) in accordance with the protocol attached to the kit. Subsequently, the buffer contained in 1.2 ml of the purified preparation obtained by the above-described method was replaced with physiological phosphate buffer (manufactured by Nissui Pharmaceutical) by ultrafiltration using NANOSEP 10K OMEGA (manufactured by PALL), and the resulting solution was filtered aseptically using HT Tuffryn Acrodisc 0.22 μm (manufactured by PALL) and used in the following experiments.

Example B-3 Test of Administration of Recombinant Protein to Cancer-Bearing Dogs (1) Antitumor Assay

The anti-tumor effect of the two kinds of recombinant proteins which were purified as described above was assessed in two individuals of cancer-bearing dogs having epidermal tumor (2 individuals having mammary gland tumor).

An equal amount of Freund's incomplete adjuvant (manufactured by Wako Pure Chemicals) was mixed with 100 μg (0.5 ml) of the recombinant canine calmegin and human calmegin proteins, respectively, to prepare therapeutic agents for a cancer(s). Each of these agents was administered to a regional lymph node in the vicinity of the tumor a total of 3 times, by carrying out the subsequent administrations 3 days and 7 days after the first administration. As a result, the tumors with a size of about 45 mm³ and 78 mm³, respectively, at the time of administration of the therapeutice agents were reduced to 27 mm³ and 46 mm³, respectively, 10 days after the first administration; 15 mm³ and 26 mm³, respectively, 20 days after the first administration; and to 7 mm³ and 15 mm³, respectively, 30 days after the first administration.

Further, to a canine patient suffering from malignant melanoma, a mixture of 100 μg (0.5 ml) of the above-described canine calmegin protein and 0.5 ml of Freund's incomplete adjuvant was administered a total of 3 times in the same manner as described above. Further, concurrently with the respective administrations, 100 μg of canine interleukin 12 was administered subcutaneously. As a result, the tumor with a size of about 38 mm³ at the time of administration of the therapeutic agent completely regressed 21 days after the first administration of the therapeutic agent.

(2) Immune Inducibility Assay

Blood from the canine patient in which the anti-tumor effect was obtained in the administration test in the above-described (1) was collected before administration of the therapeutic agent for a cancer(s) and 10 days and 30 days after the first administration. Peripheral blood mononuclear cells were isolated according to a conventional method, and by the ELISPOT assay for IFNγ using it, the immune inducibility of each administered recombinant protein was assayed.

In a 96-well plate manufactured by Millipore (MultiScreen-IP, MAIPS 4510), 100 μL/well of 70% ethanol was placed and the plate was left to stand for 5 minutes, followed by removal of the ethanol by aspiration. The plate was washed with sterile water and 300 μl/well of 200 mM Sodium Bicarbonate (pH8.2) was placed therein. After leaving it to stand for 5 minutes, Sodium Bicarbonate was removed by aspiration, and then the plate was washed. Subsequently, 0.5 μg/well of anti-canine interferon γ monoclonal antibody (manufactured by R&D, clone 142529, MAB781) mixed with 200 mM Sodium Bicarbonate was placed in wells, and the plate was incubated at 37° C. overnight to immobilize the primary antibody. After removal of the primary antibody by aspiration, 300 μL/well of a blocking solution (1% BSA-5% sucrose-200 mM Sodium Bicarbonate (pH8.2)) was added to the wells, and the plate was incubated at 4° C. overnight to block the plate. After removal of the blocking solution by aspiration, 300 μL/well of 10% fetal calf serum-containing RPMI medium (manufactured by Invitrogen) was placed in the wells, and the plate was left to stand for 5 minutes, followed by removal of the medium by aspiration. Subsequently, 5×10⁵ cells/well of the canine peripheral blood mononuclear cells suspended in 10% fetal calf serum-containing RPMI medium were placed in the plate, and 10 μL/well of the canine calmegin or human calmegin protein used in each administration was added thereto, followed by culturing the cells under the conditions of 37° C. and 5% CO₂ for 24 hours, to allow immunocytes that might exist in the peripheral blood mononuclear cells to produce interferon γ. After the culture, the medium was removed, and the wells were washed 6 times with a washing solution (0.1% Tween20-200 mM Sodium Bicarbonate (pH8.2)). In each well, 100 μL of rabbit anti-dog polyclonal antibody 1000-fold diluted with the above-described blocking solution was placed, and the resulting mixture was incubated at 4° C. overnight. After washing the wells 3 times with the above-described washing solution, 100 μL of HRP-labeled anti-rabbit antibody 1000-fold diluted with the above-described blocking solution was placed in each well, and the reaction was allowed to proceed at 37° C. for 2 hours. After washing the wells 3 times with the above-described washing solution, the resultant was colored with Konica Immunostain (manufactured by Konica), and the wells were washed with water to stop the reaction. Thereafter, the membrane was dried, and image processing of the wells was carried out, followed by counting the number of spot-forming cells (SFC) using KS ELISPOT compact system (Carl Zeiss, Inc., Germany).

As a result, in either canine patient to which canine calmegin or human calmegin was administered, peripheral blood mononuclear cells sampled before the administration showed no spots. On the other hand, in the canine patient to which canine calmegin was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 15 and 45 spots, respectively. In the canine patient to which human calmegin was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 12 and 39 spots, respectively.

From the above results, it is confirmed that immunocytes which specifically react with the administered recombinant protein and produce interferon γ were induced in all of the canine patients to which the recombinant protein was administered, and it is thought that the anti-tumor effect described in (1) was exerted by immunoreactions in which these immunocytes are mainly involved.

Example C-1 Acquisition of Novel Cancer Antigen Protein by SEREX Method

(1) Preparation of cDNA Library

Total RNA was prepared from testis tissue of a healthy dog by the Acid guanidium-Phenol-Chloroform method, and poly(A) RNA was purified using Oligotex-dT30 mRNA purification Kit (manufactured by Takara Shuzo Co., Ltd.) in accordance with the protocol attached to the kit.

Using the obtained mRNA (5 μg), a dog testis cDNA phage library was synthesized. Preparation of the cDNA phage library was carried out using cDNA Synthesis Kit, ZAP-cDNA Synthesis Kit, and ZAP-cDNA Gigapack III Gold Cloning Kit (manufactured by STRATAGENE) in accordance with the protocols attached to the kits. The size of the prepared cDNA phage library was 1.3×10⁶ pfu/ml.

(2) Screening of cDNA Library with Serum

Using the dog testis-derived cDNA phage library prepared as described above, immunoscreening was carried out. More particularly, host E. coli cells (XL1-Blue MRF′) were infected with the library such that 2,340 clones should appear on an NZY agarose plate having the size of Φ90×15 mm, and cultured at 42° C. for 3 to 4 hours to allow the phage to form plaques. The plate was covered with nitrocellulose membrane (Hybond C Extra: manufactured by GE Healthcare Bio-Science) impregnated with IPTG (isopropyl-β-D-thiogalactoside) at 37° C. for 4 hours to induce and express proteins, which were thus transferred to the membrane. Subsequently, the membrane was recovered and soaked in TBS (10 mM Tris-HCl, 150 mM NaCl; pH 7.5) containing 0.5% non-fat dry milk, followed by shaking it at 4° C. overnight to suppress non-specific reactions. This filter was allowed to react with 500-fold diluted canine patient serum at room temperature for 2 to 3 hours.

As the above-described canine patient serum, serum collected from canine patients suffering from breast cancer was used. The serum was stored at −80° C. and pretreated immediately before use. The method of the pretreatment of the serum was as follows. That is, host E. coli cells (XL1-Blue MRF′) were infected with λ ZAP Express phage to which no foreign gene was inserted, and then cultured on NZY plate medium at 37° C. overnight. Subsequently, the buffer of 0.2 M NaHCO₃, pH 8.3 containing 0.5 M NaCl was added to the plate, and the plate was left to stand at 4° C. for 15 hours, followed by collecting the supernatant as an E. coli/phage extract. Thereafter, the collected E. coli/phage extract was allowed to flow through an NHS column (manufactured by GE Healthcare Bio-Science) to immobilize proteins derived from the E. coli/phage thereon. The serum from the canine patients was allowed to flow through and react with this protein-immobilized column to remove antibodies adsorbed on E. coli and/or the phage. The serum fraction that passed through the column was 500-fold diluted with TBS containing 0.5% non-fat dry milk, and the resulting diluent was used as the material for the immunoscreening.

The membrane on which the thus treated serum and the above-described fusion protein were blotted was washed 4 times with TBS-T (0.05% Tween 20/TBS), and allowed to react with goat anti-dog IgG (Goat anti Dog IgG-h+I HRP conjugated: manufactured by BETHYL Laboratories) 5,000-fold diluted with TBS containing 0.5% non-fat dry milk as a secondary antibody at room temperature for 1 hour, followed by detection by the enzyme coloring reaction using the NBT/BCIP reaction solution (manufactured by Roche). Colonies at positions where a positive coloring reaction was observed were recovered from the NZY agarose plate having the size of Φ90×15 mm, and dissolved in 500 μl of SM buffer (100 mM NaCl, 10 mM MgClSO₄, 50 mM Tris-HCl, 0.01% gelatin; pH 7.5). The screening was repeated as a second and third screening in the same manner as described above until a single coloring reaction-positive colony was obtained, thereby isolating one positive clone after screening of 30,940 phage clones reactive with IgG in the serum.

(3) Homology Search of Isolated Antigen Gene

To subject the single positive clone isolated by the above-described method to a base sequence analysis, an operation of conversion of the phage vector to a plasmid vector was carried out. More particularly, 200 μl of a solution prepared to contain a host E. coli (XL1-Blue MRF′) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 100 μl of a purified phage solution and further with 1 μl of ExAssist helper phage (manufactured by STRATAGENE), and the reaction was allowed to proceed at 37° C. for 15 minutes. To the reaction mixture, 3 ml of LB medium was added, and the mixture was cultured at 37° C. for 2.5 to 3 hours, followed by immediate incubation in a water bath at 70° C. for 20 minutes. The mixture was then centrifuged at 4° C. at 1000×g for 15 minutes, and the supernatant was recovered as a phagemid solution. Subsequently, 200 μl of a solution prepared to contain a phagemid host E. coli (SOLR) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 10 μl of a purified phage solution, and the reaction was allowed to proceed at 37° C. for 15 minutes. Thereafter, 50 μl of the reaction mixture was plated on ampicillin (final concentration: 50 μg/ml)-containing LB agar medium, and cultured at 37° C. overnight. A single colony of transformed SOLR was recovered and cultured in ampicillin (final concentration: 50 μg/ml)-containing LB medium at 37° C., followed by purification of plasmid DNA having an insert of interest using QIAGEN plasmid Miniprep Kit (manufactured by Qiagen).

The purified plasmid was subjected to an analysis of the entire sequence of the insert by the primer walking method using the T3 primer described in SEQ ID NO:5 and the T7 primer described in SEQ ID NO:6. By this sequence analysis, the gene sequence described in SEQ ID NO:25 was obtained. Using the base sequence and the amino acid sequence of this gene, homology search against known genes was carried out using a homology search program BLAST (http://www.ncbi.nlm.nih.gov/BLAST/). As a result, it was revealed that the obtained gene has 99% homology (which was calculated only in the overlapping region) to the CEP gene described in SEQ ID NO:27 in terms of base sequence and amino acid sequence, so that the gene was judged as the CEP gene. The human homologous factor of the canine CEP was human CEP (homology to the CEP gene described in SEQ ID NO:25: base sequence, 87%; amino acid sequence, 84%). The base sequence of human CEP is shown in SEQ ID NO:29, and the amino acid sequence thereof is shown in SEQ ID NO:30.

(4) Analysis of Expression in Each Tissue

The expression of the gene, which was obtained by the above-described method, in normal tissues and various cell lines of dog and human were investigated by the RT-PCR (Reverse Transcription-PCR) method. The reverse transcription reaction was carried out as follows. That is, total RNA was extracted from 50 to 100 mg of each tissue or 5 to 10×10⁶ cells of each cell line using TRIZOL reagent (manufactured by Invitrogen) in accordance with the protocol attached to the kit. Using this total RNA, cDNA was synthesized by Superscript First-Strand Synthesis System for RT-PCR (manufactured by Invitrogen) in accordance with the protocol attached to the kit. As the cDNAs from human normal tissues (brain, hippocampus, testis, colon and placenta), Gene Pool cDNA (manufactured by Invitrogen), QUICK-Clone cDNA (manufactured by CLONTECH) and Large-Insert cDNA Library (manufactured by CLONTECH) were used. The PCR reactions were carried out as follows using primers (described in SEQ ID NOs:31 and 32) specific to the obtained gene. That is, respective reagents and the attached buffer were mixed such that the mixture should contain 0.25 μl of the sample prepared by the reverse transcription reaction, 2 μM each of the above primers, 0.2 mM each of dNTP and 0.65 U of ExTaq polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 25 μl, and the reaction was carried out with 30 cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 30 seconds using Thermal Cycler (manufactured by BIO RAD). The above-described gene-specific primers were those which amplify the regions of the 4582nd to 5124th bases of the base sequences of SEQ ID NOs:25 and 27 (canine CEP gene) and the 4610th to 5152nd bases of the base sequence of SEQ ID NO:29 (human CEP gene), and can be used for investigation of the expression of both the canine CEP gene and the human CEP gene. As a control for comparison, primers (described in SEQ ID NOs:9 and 10) specific to GAPDH were used simultaneously. As a result, as shown in FIG. 5, strong expression of the canine CEP gene was observed in testis among the normal dog tissues, and on the other hand, strong expression was observed in the canine breast cancer cell line. Expression of the human CEP gene was confirmed, as is the case with the canine CEP gene, only in testis among the human normal tissues, but the expression was detected in brain tumor, leukemia and esophagus cancer cells among human cancer cell lines, and especially, strong expression was observed in the leukemia cell line. Thus, the human CEP gene was also confirmed to be specifically expressed in testis and cancer cells.

In FIG. 5, reference numeral 1 in the ordinate indicates the expression pattern of the CEP gene, and reference numeral 2 indicates the expression pattern of the GAPDH gene as a control for comparison.

Example C-2 Preparation of Canine and Human CEPs (1) Preparation of Recombinant Protein

Based on the gene of SEQ ID NO:25 obtained in Example C-1, a recombinant protein was prepared by the following method. Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the vector that was prepared from the phagemid solution obtained in Example C-1 and was subjected to the sequence analysis, 0.4 μM each of two kinds of primers having BamHI and SalI restriction sites (described in SEQ ID NOs:33 and 34), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 5 seconds and 72° C. for 7 minutes using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:26. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 7.0 kbp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes BamHI and SalI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30a (manufactured by Novagen) that had been treated with BamHI and SalI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG. In the same manner, based on the gene of SEQ ID NO:27, using the canine testis cDNA as a template and two kinds of primers having BamHI and SalI restriction sites (SEQ ID NOs:33 and 35), a recombinant protein of the registered canine CEP gene was prepared. The above-described two kinds of primers were those which amplify the region of about 7.8 kbp encoding the entire amino acid sequence of SEQ ID NO:28.

Further, based on the gene of SEQ ID NO:29, a recombinant protein of the human homologous gene was prepared by the following method. Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the cDNA prepared in Example C-1 whose expression could be confirmed by the RT-PCR method in various tissues/cells, 0.4 μM each of two kinds of primers having BamHI and SalI restriction sites (described in SEQ ID NOs:36 and 37), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 5 seconds and 72° C. for 7 minutes using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:30. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 7.0 kbp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes BamHI and SalI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30a (manufactured by Novagen) that had been treated with BamHI and SalI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG.

(2) Purification of Recombinant Protein

The above-obtained recombinant E. coli cells that expressed SEQ ID NO:25, SEQ ID NO:27, and SEQ ID NO:29, respectively, were cultured in 30 μg/ml kanamycin-containing LB medium at 37° C. until the absorbance at 600 nm reached about 0.7, and then isopropyl-β-D-1-thiogalactopyranoside was added thereto such that its final concentration should be 1 mM, followed by culturing them at 30° C. for 20 hours. Subsequently, the cells were collected by centrifugation at 4,800 rpm for 10 minutes. The pellet of the cells was suspended in phosphate-buffered saline and further subjected to centrifugation at 4,800 rpm for 10 minutes to wash the cells.

The cells were suspended in phosphate-buffered saline and subjected to sonication on ice. The sonicated solution of E. coli was centrifuged at 7000 rpm for 20 minutes to obtain the supernatant as the soluble fraction and the precipitate as the insoluble fraction. The insoluble fraction was suspended in 4% Triton X-100 solution and the resulting suspension was centrifuged at 7000 rpm for 20 minutes. This operation was repeated twice and an operation of removal of proteases was carried out. The residue was suspended in 8 M urea-containing 10 mM Tris-HCl, 100 mM phosphate buffer (hereinafter referred to as 8 M urea solution) and a protease inhibitor cocktail solution, and the resulting suspension was left to stand at 4° C. for 20 hours to denature proteins.

Thereafter, the suspension was centrifuged at 7,000 rpm for 20 minutes, and the obtained soluble fraction was placed in a nickel chelate column prepared by a conventional method (carrier: Chelating Sepharose (trademark) Fast Flow (GE Health Care); column volume: 5 mL; equilibration buffer: 8M urea solution), followed by leaving it to stand at 4° C. overnight. The supernatant was recovered by centrifugation of this column carrier at 1,500 rpm for 5 minutes, and the column carrier was suspended in phosphate-buffered saline, followed by refilling the column with the resulting suspension. The fraction that was not adsorbed to the column was washed away with 5 column volumes of 8 M urea solution, 10 column volumes of 0.5 M sodium chloride-containing 0.1 M acetate buffer (pH 5.0) and 10 mM imidazole-containing 20 mM phosphate buffer (pH 8.0), and elution was immediately carried out with a five-step density gradient of 100 mM-500 mM imidazole to obtain a purified fraction, which was used as the material for administration tests thereafter. The proteins of interest in respective eluted fractions were confirmed by Coomassie staining carried out according to a conventional method. Among these, the recombinant canine CEP described in SEQ ID NO:26 is shown in FIG. 6.

To 1 ml of a reaction buffer (20 mM Tris-HCl, 50 mM NaCl, 2 mM CaCl₂; pH 7.4), 200 μl of the purified preparation obtained by the above-described method was aliquoted, and 2 μl of enterokinase (manufactured by Novagen) was then added thereto, followed by leaving it to stand at room temperature overnight to cleave His tag. The resulting product was purified using Enterokinase Cleavage Capture Kit (manufactured by Novagen) in accordance with the protocol attached to the kit. Subsequently, the buffer contained in 1.2 ml of the purified preparation obtained by the above-described method was replaced with physiological phosphate buffer (manufactured by Nissui Pharmaceutical) by ultrafiltration using NANOSEP 10K OMEGA (manufactured by PALL), and the resulting solution was filtered aseptically using HT Tuffryn Acrodisc 0.22 μm (manufactured by PALL) and used in the following experiments.

Example C-3 Test of Administration of Recombinant Protein to Cancer-Bearing Dogs (1) Antitumor Assay

The anti-tumor effect of the two kinds of recombinant proteins which were purified as described above was assessed in two individuals of cancer-bearing dogs having epidermal tumor (2 individuals having perianal adenoma).

An equal amount of Freund's incomplete adjuvant (manufactured by Wako Pure Chemicals) was mixed with 100 μg (0.5 ml) each of the recombinant canine CEP described in SEQ ID NO:26 and human CEP purified as described above to prepare therapeutic agents for a cancer(s). Each of these agents was administered to a regional lymph node in the vicinity of the tumor a total of 3 times, by carrying out the subsequent administrations 3 days and 7 days after the first administration. As a result, the tumors with a size of about 87 mm³ and 69 mm³ at the time of administration of the therapeutic agents, respectively, were reduced to 69 mm³ and 56 mm³, respectively, 10 days after the first administration; 24 mm³ and 31 mm³, respectively, 20 days after the first administration; and to 10 mm³ and 8 mm³, respectively, 30 days after the first administration of the therapeutic agent.

Further, to a canine patient suffering from mammary adenocarcinoma, a mixture of 100 μg (0.5 ml) of the canine CEP protein described in SEQ ID NO:26 with 0.5 ml of Freund's incomplete adjuvant was administered a total of 3 times in the same manner as described above. Further, concurrently with the respective administrations, 10 MU of “Intercat” which is a recombinant feline interferon was administered subcutaneously. As a result, the tumor with a size of about 126 mm³ at the time of administration of the therapeutic agent completely regressed 26 days after the first administration of the therapeutic agent. Similarly, in the case where the canine CEP described in SEQ ID NO:28 was used, an anti-tumor effect was also observed in a cancer-bearing dog.

Further, to a canine patient of mastocytoma, a mixture of 100 μg (0.5 ml) of the canine CEP protein described in SEQ ID NO:26 with 0.5 ml of Freund's incomplete adjuvant was administered a total of 3 times in the same manner as described above. Further, concurrently with the respective administrations, 100 μg of canine interleukin-12 was subcutaneously administered. As a result, the tumor with a size of about 83 mm³ at the time of administration of the therapeutic agent completely regressed 18 days after the first administration of the therapeutic agent.

(2) Immune Inducibility Assay

Blood from the canine patient suffering from perianal adenoma in which the anti-tumor effect was obtained in the administration test in the above-described (1) was collected before administration of the therapeutic agent for a cancer(s) and 10 days and 30 days after the first administration. Peripheral blood mononuclear cells were isolated according to a conventional method, and by the ELISPOT assay for IFNγ using it, the immune inducibility of each administered protein was assayed.

In a 96-well plate manufactured by Millipore (MultiScreen-IP, MAIPS 4510), 100 μL/well of 70% ethanol was placed and the plate was left to stand for 5 minutes, followed by removal of the ethanol by aspiration. The plate was washed with sterile water and 300 μl/well of 200 mM Sodium Bicarbonate (pH8.2) was placed therein. After leaving it to stand for 5 minutes, Sodium Bicarbonate was removed by aspiration, and then the plate was washed. Subsequently, 0.5 μl/well of anti-canine interferon γ monoclonal antibody (manufactured by R&D, clone 142529, MAB781) mixed with 200 mM Sodium Bicarbonate was placed in wells, and the plate was incubated at 37° C. overnight to immobilize the primary antibody. After removal of the primary antibody by aspiration, 300 μL/well of a blocking solution (1% BSA-5% sucrose-200 mM Sodium Bicarbonate (pH8.2)) was added to the wells, and the plate was incubated at 4° C. overnight to block the plate. After removal of the blocking solution by aspiration, 300 μL/well of 10% fetal calf serum-containing RPMI medium (manufactured by Invitrogen) was placed in the wells, and the plate was left to stand for 5 minutes, followed by removal of the medium by aspiration. Subsequently, 5×10⁵ cells/well of the canine peripheral blood mononuclear cells suspended in 10% fetal calf serum-containing RPMI medium were placed in the plate, and 10 μL/well of the canine CEP described in SEQ ID NO:26 or the human CEP used in each administration was added thereto, followed by culturing the cells under the conditions of 37° C. and 5% CO₂ for 24 hours, to allow immunocytes that might exist in the peripheral blood mononuclear cells to produce interferon γ. After the culture, the medium was removed, and the wells were washed 6 times with a washing solution (0.1% Tween20-200 mM Sodium Bicarbonate (pH8.2)). In each well, 100 μL of rabbit anti-canine polyclonal antibody 1000-fold diluted with the above-described blocking solution was placed, and the plate was incubated at 4° C. overnight. After washing the wells 3 times with the above-described washing solution, 100 μL of HRP-labeled anti-rabbit antibody 1000-fold diluted with the above-described blocking solution was placed in each well, and the reaction was allowed to proceed at 37° C. for 2 hours. After washing the wells 3 times with the above-described washing solution, the resultant was colored with Konica Immunostain (manufactured by Konica), and the wells were washed with water to stop the reaction. Thereafter, the membrane was dried, and image processing of the wells was carried out, followed by counting the number of spot-forming cells (SFC) using KS ELISPOT compact system (Carl Zeiss, Inc., Germany).

As a result, in either canine patient to which the canine CEP described in SEQ ID NO: 26 or the human CEP was administered, peripheral blood mononuclear cells sampled before the administration showed no spots. On the other hand, in the canine patient to which the canine CEP was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 23 and 52 spots, respectively. In the canine patient to which the human CEP was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 19 and 49 spots, respectively.

From the above results, it is confirmed that immunocytes which specifically react with the administered recombinant protein and produce interferon γ were induced in all of the canine patients to which the recombinant protein was administered, and it is thought that the anti-tumor effect described in (1) was exerted by immunoreactions in which these immunocytes are mainly involved.

Example D-1 Acquisition of Novel Cancer Antigen Protein by SEREX Method

(1) Preparation of cDNA Library

Total RNA was prepared from testis tissue of a healthy dog by the Acid guanidium-Phenol-Chloroform method, and poly(A) RNA was purified using Oligotex-dT30 mRNA purification Kit (manufactured by Takara Shuzo Co., Ltd.) in accordance with the protocol attached to the kit.

Using the obtained mRNA (5 μg), a dog testis cDNA phage library was synthesized. Preparation of the cDNA phage library was carried out using cDNA Synthesis Kit, ZAP-cDNA Synthesis Kit, and ZAP-cDNA Gigapack III Gold Cloning Kit (manufactured by STRATAGENE) in accordance with the protocols attached to the kits. The size of the prepared cDNA phage library was 1.3×10⁶ pfu/ml.

(2) Screening of cDNA Library with Serum

Using the dog testis-derived cDNA phage library prepared as described above, immunoscreening was carried out. More particularly, host E. coli cells (XL1-Blue MRF′) were infected with the library such that 2,340 clones should appear on an NZY agarose plate having the size of Φ90×15 mm, and cultured at 42° C. for 3 to 4 hours to allow the phage to form plaques. The plate was covered with nitrocellulose membrane (Hybond C Extra: manufactured by GE Healthcare Bio-Science) impregnated with IPTG (isopropyl-β-D-thiogalactoside) at 37° C. for 4 hours to induce and express proteins, which were thus transferred to the membrane. Subsequently, the membrane was recovered and soaked in TBS (10 mM Tris-HCl, 150 mM NaCl; pH 7.5) containing 0.5% non-fat dry milk, followed by shaking at 4° C. overnight to suppress non-specific reactions. This filter was allowed to react with 500-fold diluted canine patient serum at room temperature for 2 to 3 hours.

As the above-described canine patient serum, serum collected from canine patients suffering from breast cancer was used. The serum was stored at −80° C. and pretreated immediately before use. The method of the pretreatment of the serum was as follows. That is, host E. coli cells (XL1-Blue MRF′) were infected with λ ZAP Express phage to which no foreign gene was inserted, and then cultured on NZY plate medium at 37° C. overnight. Subsequently, the buffer of 0.2 M NaHCO₃, pH 8.3 containing 0.5 M NaCl was added to the plate, and the plate was left to stand at 4° C. for 15 hours, followed by collecting the supernatant as an E. coli/phage extract. Thereafter, the collected E. coli/phage extract was allowed to flow through an NHS column (manufactured by GE Healthcare Bio-Science) to immobilize proteins derived from the E. coli/phage thereon. The serum from the canine patients was allowed to flow through and react with this protein-immobilized column to remove antibodies adsorbed on E. coli and/or the phage. The serum fraction that passed through the column was 500-fold diluted with TBS containing 0.5% non-fat dry milk, and the resulting diluent was used as the material for the immunoscreening.

The membrane on which the thus treated serum and the above-described fusion protein were blotted was washed 4 times with TBS-T (0.05% Tween 20/TBS), and allowed to react with goat anti-dog IgG (Goat anti Dog IgG-h+I HRP conjugated: manufactured by BETHYL Laboratories) 5,000-fold diluted with TBS containing 0.5% non-fat dry milk as a secondary antibody at room temperature for 1 hour, followed by detection by the enzyme coloring reaction using the NBT/BCIP reaction solution (manufactured by Roche). Colonies at positions where a positive coloring reaction was observed were recovered from the NZY agarose plate having the size of Φ90×15 mm, and dissolved in 500 μl of SM buffer (100 mM NaCl, 10 mM MgClSO₄, 50 mM Tris-HCl, 0.01% gelatin; pH 7.5). The screening was repeated as a second and third screening in the same manner as described above until a single coloring reaction-positive colony was obtained, thereby isolating one positive clone after screening of 30,940 phage clones reactive with IgG in the serum.

(3) Homology Search of Isolated Antigen Gene

To subject the single positive clone isolated by the above-described method to a base sequence analysis, an operation of conversion of the phage vector to a plasmid vector was carried out. More particularly, 200 μl of a solution prepared to contain a host E. coli (XL1-Blue MRF′) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 100 μl of a purified phage solution and further with 1 μl of ExAssist helper phage (manufactured by STRATAGENE), and the reaction was allowed to proceed at 37° C. for 15 minutes. To the reaction mixture, 3 ml of LB medium was added, and the mixture was cultured at 37° C. for 2.5 to 3 hours, followed by immediate incubation in a water bath at 70° C. for 20 minutes. The mixture was then centrifuged at 4° C. at 1000×g for 15 minutes, and the supernatant was recovered as a phagemid solution. Subsequently, 200 μl of a solution prepared to contain a phagemid host E. coli (SOLR) such that the absorbance OD₆₀₀ should be 1.0 was mixed with 10 μl of a purified phage solution, and the reaction was allowed to proceed at 37° C. for 15 minutes. Thereafter, 50 μl of the reaction mixture was plated on ampicillin (final concentration: 50 μg/ml)-containing LB agar medium, and cultured at 37° C. overnight. A single colony of transformed SOLR was recovered and cultured in ampicillin (final concentration: 50 μg/ml)-containing LB medium at 37° C., followed by purification of plasmid DNA having an insert of interest using QIAGEN plasmid Miniprep Kit (manufactured by Qiagen).

The purified plasmid was subjected to an analysis of the entire sequence of the insert by the primer walking method using the T3 primer described in SEQ ID NO:5 and the T7 primer described in SEQ ID NO:6. By this sequence analysis, the gene sequence described in SEQ ID NO:38 was obtained. Using the base sequence and the amino acid sequence of this gene, homology search against known genes was carried out using a homology search program BLAST (http://www.ncbi.nlm.nih.gov/BLAST/). As a result, it was revealed that the obtained gene is the TRIP11 gene. The human homologous factor of canine TRIP11 was human TRIP11 (homology: base sequence, 88%; amino acid sequence, 86%). The base sequence of human TRIP11 is shown in SEQ ID NO:40, and the amino acid sequence thereof is shown in SEQ ID NO:41.

(4) Analysis of Expression in Each Tissue

The expression of the gene, which was obtained by the above-described method, in normal tissues and various cell lines of dog and human were investigated by the RT-PCR (Reverse Transcription-PCR) method. The reverse transcription reaction was carried out as follows. That is, total RNA was extracted from 50 to 100 mg of each tissue or 5 to 10×10⁶ cells of each cell line using TRIZOL reagent (manufactured by Invitrogen) in accordance with the protocol attached to the kit. Using this total RNA, cDNA was synthesized by Superscript First-Strand Synthesis System for RT-PCR (manufactured by Invitrogen) in accordance with the protocol attached to the kit. As the cDNAs from human normal tissues (brain, hippocampus, testis, colon and placenta), Gene Pool cDNA (manufactured by Invitrogen), QUICK-Clone cDNA (manufactured by CLONTECH) and Large-Insert cDNA Library (manufactured by CLONTECH) were used. The PCR reactions were carried out as follows using primers (described in SEQ ID NOs:42 and 43) specific to the obtained gene. That is, respective reagents and the attached buffer were mixed such that the mixture should contain 0.25 μl of the sample prepared by the reverse transcription reaction, 2 μM each of the above primers, 0.2 mM each of dNTP and 0.65 U of ExTaq polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 25 and the reaction was carried out with 30 cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 1.5 minutes using Thermal Cycler (manufactured by BIO RAD). The above-described gene-specific primers were those which amplify the regions of the 1519th to 2957th bases of the base sequence of SEQ ID NO:38 (canine TRIP11 gene) and the 1872nd to 3310th bases of the base sequence of SEQ ID NO:40 (human TRIP11 gene), and can be used for investigation of the expression of both the canine TRIP11 gene and the human TRIP11 gene. As a control for comparison, primers (described in SEQ ID NOs:9 and 10) specific to GAPDH were used simultaneously. As a result, as shown in FIG. 7, strong expression of the canine TRIP11 gene was observed in testis among the normal dog tissues, and on the other hand, strong expression was observed in the canine breast cancer cell line. Expression of the human gene was confirmed, as is the case with the canine TRIP11 gene, only in testis among the human normal tissues, but the expression was detected in many types of cancer cell lines such as brain tumor, leukemia, breast cancer, lung cancer and esophagus cancer cell lines among human cancer cell lines. Thus, the human TRIP11 gene was also confirmed to be specifically expressed in testis and cancer cells.

In FIG. 7, reference numeral 1 in the ordinate indicates the expression pattern of the TRIP11 gene, and reference numeral 2 indicates the expression pattern of the GAPDH gene as a control for comparison.

Example D-2 Preparation of Canine and Human TRIP11 Proteins (1) Preparation of Recombinant Protein

Based on the gene of SEQ ID NO:38 obtained in Example D-1, a recombinant protein was prepared by the following method. NO:Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the vector which was prepared from the phagemid solution obtained in Example D-1 and was subjected to the sequence analysis, 0.4 μM each of two kinds of primers having SalI and XhoI restriction sites (described in SEQ ID NOs:44 and 45), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 5 seconds and 72° C. for 6 minutes using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:39. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 6.0 kbp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes SalI and XhoI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30b (manufactured by Novagen) that had been treated with SalI and XhoI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG.

Further, based on the gene of SEQ ID NO:40, a recombinant protein of the human homologous gene was prepared by the following method. Respective reagents and the attached buffer were mixed such that the mixture should contain 1 μl of the cDNA prepared in Example D-1 whose expression could be confirmed by the RT-PCR method in various tissues/cells, 0.4 μM each of two kinds of primers having NdeI and KpnI restriction sites (described in SEQ ID NOs:46 and 47), 0.2 mM dNTP and 1.25 U of PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) in a total volume of 50 μl, and PCR was carried out with 30 cycles of 98° C. for 10 seconds, 55° C. for 5 seconds and 72° C. for 6 minutes using Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those which amplify the region encoding the entire amino acid sequence of SEQ ID NO:41. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 6.0 kbp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and plasmids were recovered thereafter, followed by confirming, by sequencing, that the amplified gene fragment matches the sequence of interest. The plasmid that matched the sequence of interest was treated with restriction enzymes NdeI and KpnI and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30b (manufactured by Novagen) that had been treated with NdeI and KpnI. Usage of this vector enables production of a His-tag fusion recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression of the protein of interest was induced in E. coli with 1 mM IPTG.

(2) Purification of Recombinant Proteins

The above-obtained recombinant E. coli cells that expressed SEQ ID NO:38 and SEQ ID NO:40, respectively, were cultured in 30 μg/ml kanamycin-containing LB medium at 37° C. until the absorbance at 600 nm reached about 0.7, and then isopropyl-3-D-1-thiogalactopyranoside was added thereto such that its final concentration should be 1 mM, followed by culturing them at 30° C. for 20 hours. Subsequently, the cells were collected by centrifugation at 4,800 rpm for 10 minutes. The pellet of the cells was suspended in phosphate-buffered saline and further subjected to centrifugation at 4,800 rpm for 10 minutes to wash the cells.

The obtained pellet of E. coli cells was suspended in phosphate-buffered saline and subjected to sonication on ice. The sonicated solution of E. coli was centrifuged at 7,000 rpm for 15 minutes to obtain the supernatant as the soluble fraction and the precipitate as the insoluble fraction.

The insoluble fraction was suspended in 4% Triton X-100 solution and the resulting suspension was centrifuged at 7,000 rpm for 10 minutes. This operation was repeated twice and an operation of removal of proteases was carried out. Thereafter, the residue was suspended in phosphate-buffered saline and an operation of removal of the surfactant was carried out.

The residue was suspended in 6M guanidine hydrochloride-containing 20 mM phosphate buffer (pH 8.0), and the resulting suspension was left to stand at 4° C. for 20 hours to denature proteins. Thereafter, the suspension was centrifuged at 7,000 rpm for 20 minutes, and the obtained soluble fraction was placed in a nickel chelate column prepared by a conventional method (carrier: Chelating Sepharose (trademark) Fast Flow (GE Health Care); column volume: 5 mL; equilibration buffer: 6M guanidine hydrochloride-containing 20 mM phosphate buffer (pH 8.0)). The fraction that was not adsorbed to the column was washed away with 10 column volumes of 6 M sodium chloride-containing 20 mM phosphate buffer (pH 8.0) and 10 mM imidazole-containing 20 mM phosphate buffer (pH 8.0), and elution was immediately carried out with a four-step density gradient of 50 mM-500 mM imidazole to obtain a purified fraction, which was used as the material for administration tests thereafter. The proteins of interest in the eluted fractions were confirmed by Coomassie staining carried out according to a conventional method. Among these, the canine TRIP11 protein is shown in FIG. 8.

To 1 ml of a reaction buffer (20 mM Tris-HCl, 50 mM NaCl, 2 mM CaCl₂; pH 7.4), 200 μl of the purified preparation obtained by the above-described method was aliquoted, and 2 μl of enterokinase (manufactured by Novagen) was then added thereto, followed by leaving it to stand at room temperature overnight to cleave His tag. The resulting product was purified using Enterokinase Cleavage Capture Kit (manufactured by Novagen) in accordance with the protocol attached to the kit. Subsequently, the buffer contained in 1.2 ml of the purified preparation obtained by the above-described method was replaced with physiological phosphate buffer (manufactured by Nissui Pharmaceutical) by ultrafiltration using NANOSEP 10K OMEGA (manufactured by PALL), and the resulting solution was filtered aseptically using HT Tuffryn Acrodisc 0.22 μm (manufactured by PALL) and used in the following experiments.

Example D-3 Test of Administration of Recombinant Protein to Cancer-Bearing Dogs (1) Antitumor Assay

The anti-tumor effect of the two kinds of recombinant proteins which were purified as described above was assessed in two individuals of cancer-bearing dogs having epidermal tumor (2 individuals having mammary gland tumor).

Therapeutic agents for a cancer(s) were prepared by mixing 0.5 ml of Freund's incomplete adjuvant (manufactured by Wako Pure Chemicals) with 100 μg (0.5 ml) of the recombinant canine TRIP11 and human TRIP11 proteins, respectively, purified as described above. Each of these agents was administered to a regional lymph node in the vicinity of the tumor a total of 3 times, by carrying out the subsequent administrations 3 days and 7 days after the first administration. As a result, the tumors with a size of about 75 mm³ and 102 mm³, respectively, at the time of administration of the therapeutic agents were reduced to 63 mm³ and 85 mm³, respectively, 10 days after the first administration; 35 mm³ and 42 mm³, respectively, 20 days after the first administration; and to 15 mm³ and 19 mm³, respectively, 30 days after the first administration of the therapeutic agent for a cancer(s).

Further, to a canine patient suffering from mastocytoma, a mixture of 100 μg (0.5 ml) of the canine TRP11 protein with 0.5 ml of Freund's incomplete adjuvant was administered a total of 3 times in the same manner as described above. Concurrently with the respective administrations, 100 μg of canine interleukin-12 was subcutaneously administered. As a result, the tumor with a size of about 165 mm³ at the time of administration of the therapeutic agent completely regressed 23 days after the first administration of the therapeutic agent.

(2) Immune Inducibility Assay

Blood from the canine patient suffering from mammary gland tumor in which the anti-tumor effect was obtained in the administration test in the above-described (1) was collected. Peripheral blood mononuclear cells were isolated according to a conventional method, and by the ELISPOT assay for IFNγ using it, the immune inducibility of each administered protein was assayed.

In a 96-well plate manufactured by Millipore (MultiScreen-IP, MAIPS 4510), 100 μL/well of 70% ethanol was placed and the plate was left to stand for 5 minutes, followed by removal of the ethanol by aspiration. The plate was washed with sterile water and 300 μl/well of 200 mM Sodium Bicarbonate (pH8.2) was placed therein. After leaving it to stand for 5 minutes, Sodium Bicarbonate was removed by aspiration, and then the plate was washed. Subsequently, 0.5 μg/well of anti-canine interferon γ monoclonal antibody (manufactured by R&D, clone 142529, MAB781) mixed with 200 mM Sodium Bicarbonate was placed in wells, and the plate was incubated at 37° C. overnight to immobilize the primary antibody. After removal of the primary antibody by aspiration, 300 μL/well of a blocking solution (1% BSA-5% sucrose-200 mM Sodium Bicarbonate (pH8.2)) was added to the wells, and the plate was incubated at 4° C. overnight to block the plate. After removal of the blocking solution by aspiration, 300 μL/well of 10% fetal calf serum-containing RPMI medium (manufactured by Invitrogen) was placed in the wells and the plate was left to stand for 5 minutes, followed by removal of the medium by aspiration. Subsequently, 5×10⁵ cells/well of the canine peripheral blood mononuclear cells suspended in 10% fetal calf serum-containing RPMI medium were placed in the plate, and 10 μL/well of the canine TRIP11 or the human TRIP11 protein used in each administration was added thereto, followed by culturing the cells under the conditions of 37° C. and 5% CO₂ for 24 hours, to allow immunocytes that might exist in the peripheral blood mononuclear cells to produce interferon γ. After the culture, the medium was removed, and the wells were washed 6 times with a washing solution (0.1% Tween20-200 mM Sodium Bicarbonate (pH8.2)). In each well, 100 μL of rabbit anti-dog polyclonal antibody 1000-fold diluted with the above-described blocking solution was placed, and the plate was incubated at 4° C. overnight. After washing the wells 3 times with the above-described washing solution, 100 μL of HRP-labeled anti-rabbit antibody 1,000-fold diluted with the above-described blocking solution was placed in each well, and the reaction was allowed to proceed at 37° C. for 2 hours. After washing the wells 3 times with the above-described washing solution, the resultant was colored with Konica Immunostain (manufactured by Konica), and the wells were washed with water to stop the reaction. Thereafter, the membrane was dried, and image processing of the wells was carried out, followed by counting the number of spot-forming cells (SFC) using KS ELISPOT compact system (Carl Zeiss, Inc., Germany).

As a result, in either canine patient to which the canine TRIP11 protein or the human TRIP11 protein was administered, peripheral blood mononuclear cells sampled before the administration showed no spots. On the other hand, in the canine patient to which the canine TRIP11 was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 26 and 65 spots, respectively. In the canine patient to which the human TRIP11 was administered, peripheral blood mononuclear cells sampled 10 days and 30 days after the administration showed 31 and 72 spots, respectively.

From the above results, it is confirmed that immunocytes which specifically react with the administered recombinant protein and produce interferon γ were induced in all of the canine patients to which the recombinant protein was administered, and it is thought that the anti-tumor effect described in the above-described (1) was exerted by immunoreactions in which these immunocytes are mainly involved. 

1. A method for inducing immunity, said method comprising administering to an individual an effective amount of any one of the polypeptides (a) to (c) below, said polypeptide having an immunity-inducing activity: (a) a polypeptide consisting of not less than 7 consecutive amino acids of the amino acid sequence shown in SEQ ID NO: 2 or 4 in SEQUENCE LISTING; (b) a polypeptide having a homology of not less than 80% to the polypeptide (a) and consisting of not less than 7 amino acids; and (c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence thereof.
 2. A method for inducing immunity, said method comprising administering to an individual an effective amount of a recombinant vector which comprises a polynucleotide encoding an immunity-inducing polypeptide selected from any one of the polypeptides (a) to (c) below, said recombinant vector being capable of expressing said polypeptide in vivo: (a) a polypeptide consisting of not less than 7 consecutive amino acids of the amino acid sequence shown in SEQ ID NO:2 or 4 in SEQUENCE LISTING; (b) a polypeptide having a homology of not less than 80% to the polypeptide (a) and consisting of not less than 7 amino acids; and (c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence thereof. 